feat: iCal export, grade calculator, countdown pulse, session logout

- iCal feed at /api/ical/:token.ics — timetable (recurring), homework,
  class events, countdowns; subscribe in Google/Apple/Outlook Calendar
- POST /api/ical-token + /api/ical-token/regenerate for token management
- Grade calculator panel in Noten overlay: per-subject weighted average
  + "what score do I need?" solver (picks correct GRADE_WEIGHTS per type)
- Countdown urgency: items ≤2 days pulse red via CSS animation
- POST /api/me/logout-other — invalidates all other sessions by bumping
  token_version, re-issues JWT for current session
- Settings: iCal URL section + copy button; session management section
- Migration: users.ical_token, grades.created_at

public/app.html

@@ -551,6 +551,20 @@ main {
 .grade-avg-val { font-size: 24px; font-weight: 800; color: var(--blue); letter-spacing: -1px; }
 .grade-avg-sub { font-size: 10px; color: var(--text-subtle); margin-top: 2px; }
 
+.grade-calc-panel {
+  margin-top: 12px; padding: 12px;
+  background: var(--surface-2); border: 1px solid var(--border);
+  border-radius: var(--r); display: none;
+}
+.grade-calc-panel.open { display: block; }
+.grade-calc-row { display:flex; gap:6px; flex-wrap:wrap; margin-bottom:8px; }
+.grade-calc-row select, .grade-calc-row input {
+  height:28px; padding:0 8px; border:1px solid var(--border);
+  border-radius:var(--r-sm); font-size:12px; background:var(--surface);
+  color:var(--text); font-family:inherit; min-width:0;
+}
+.grade-calc-result { font-size:13px; color:var(--text-2); min-height:18px; }
+
 /* ── ABSENCES ────────────────────────────────────────────── */
 
 .ab-item {
@@ -596,6 +610,9 @@ main {
 .cd-item:last-child { border-bottom: none; }
 .cd-days { font-size: 18px; font-weight: 800; color: var(--blue); min-width: 36px; text-align: center; letter-spacing: -1px; font-variant-numeric: tabular-nums; line-height: 1; }
 .cd-days.past { color: var(--text-subtle); font-size: 14px; }
+@keyframes cd-pulse { 0%,100%{box-shadow:0 0 0 0 rgba(220,38,38,0)} 50%{box-shadow:0 0 0 5px rgba(220,38,38,.18)} }
+.cd-item.urgent { border-radius:var(--r-sm); border-bottom:1px solid rgba(220,38,38,.25); animation:cd-pulse 2s ease-in-out infinite; }
+.cd-item.urgent .cd-days { color:var(--red)!important; }
 .cd-info { flex: 1; }
 .cd-title { font-size: 13px; font-weight: 500; color: var(--text); }
 .cd-date { font-size: 11px; color: var(--text-muted); margin-top: 1px; }
@@ -1108,11 +1125,31 @@ footer {
   <div class="card-head">
     <div class="card-title"><i data-lucide="graduation-cap" aria-hidden="true"></i> Noten</div>
     <div class="card-actions">
+      <button class="add-btn" onclick="toggleGradeCalc()" id="btn-grade-calc">Rechner</button>
       <button class="add-btn" onclick="openModal('grades')">+ Note</button>
       <button class="card-expand-btn" onclick="closeOverlay()" title="Schließen"><i data-lucide="x"></i></button>
     </div>
   </div>
-  <div class="card-body" id="list-grades"></div>
+  <div class="card-body" style="padding:0;display:flex;flex-direction:column">
+    <div class="grade-calc-panel" id="grade-calc-panel" style="margin:12px 12px 0">
+      <div style="font-size:11px;font-weight:600;color:var(--text-muted);text-transform:uppercase;letter-spacing:.5px;margin-bottom:8px">Notenrechner</div>
+      <div class="grade-calc-row">
+        <select id="calc-subject" onchange="updateGradeCalc()" style="flex:1">
+          <option value="">Alle Fächer</option>
+        </select>
+        <select id="calc-type" onchange="updateGradeCalc()">
+          <option value="schulaufgabe">Schulaufgabe</option>
+          <option value="kurzarbeit">Kurzarbeit</option>
+          <option value="stegreifaufgabe">Stegreifaufgabe</option>
+          <option value="muendlich">Mündlich</option>
+          <option value="sonstiges">Sonstiges</option>
+        </select>
+        <input type="number" id="calc-target" min="1" max="6" step="0.1" placeholder="Ziel (1–6)" style="width:90px" oninput="updateGradeCalc()">
+      </div>
+      <div class="grade-calc-result" id="calc-result"></div>
+    </div>
+    <div id="list-grades" style="padding:12px;flex:1"></div>
+  </div>
 </div>
 
 <div class="card ov-card" id="card-files" style="display:none">
@@ -1594,6 +1631,25 @@ footer {
       </div>
     </div>
 
+    <div class="settings-section">
+      <div class="settings-label">Kalender-Export (iCal)</div>
+      <p style="font-size:12px;color:var(--text-muted);margin-bottom:8px">Abonniere deinen Stundenplan, Hausaufgaben und Events in Google Calendar, Apple Calendar oder Outlook.</p>
+      <div style="display:flex;gap:8px;flex-wrap:wrap">
+        <button class="btn-save" style="font-size:12px;padding:5px 12px" onclick="getIcalUrl()">URL generieren</button>
+        <button class="btn-cancel" style="font-size:12px;padding:5px 12px" onclick="regenIcalUrl()">Neu generieren</button>
+      </div>
+      <div id="ical-url-row" style="display:none;margin-top:8px">
+        <input id="ical-url" type="text" readonly style="width:100%;font-size:11px;padding:5px 8px;border:1px solid var(--border);border-radius:var(--r-sm);background:var(--surface-2);color:var(--text);font-family:monospace" onclick="this.select()">
+        <button class="btn-cancel" style="font-size:11px;padding:3px 10px;margin-top:4px" onclick="copyIcalUrl()">Kopieren</button>
+      </div>
+    </div>
+
+    <div class="settings-section">
+      <div class="settings-label">Sitzungsverwaltung</div>
+      <p style="font-size:12px;color:var(--text-muted);margin-bottom:8px">Alle anderen Geräte und Browser werden sofort abgemeldet. Du bleibst eingeloggt.</p>
+      <button class="btn-cancel" style="font-size:12px;padding:5px 12px" onclick="logoutOther()">Andere Geräte abmelden</button>
+    </div>
+
     <div class="settings-section">
       <div class="danger-zone">
         <p>Account und alle gespeicherten Daten werden <strong>unwiderruflich gelöscht</strong>.</p>
@@ -1902,6 +1958,8 @@ function renderHW(data){
 
 // ── GRADES ────────────────────────────────────────────────────
 function renderGrades(data){
+  gradeCalcData=data;
+  if(document.getElementById('grade-calc-panel')?.classList.contains('open')) updateGradeCalc();
   const el=document.getElementById('list-grades');
   if(!data.length){el.innerHTML='<div class="empty">Keine Noten eingetragen</div>';return;}
   const rows=data.map(g=>{
@@ -2012,7 +2070,8 @@ function renderCountdowns(data){
   if(!data.length){el.innerHTML='<div class="empty">Keine Countdowns</div>';return;}
   el.innerHTML=[...data].sort((a,b)=>(a.target_date||'').localeCompare(b.target_date||'')).map(c=>{
     const d=daysUntil(c.target_date);
-    return `<div class="cd-item">
+    const urgent=d>=0&&d<=2?' urgent':'';
+    return `<div class="cd-item${urgent}">
       <div class="cd-days ${d<0?'past':''}">${d<0?'✓':d}</div>
       <div class="cd-info"><div class="cd-title">${esc(c.title)}</div><div class="cd-date">${fmtDate(c.target_date)}</div></div>
       <button class="del-btn" onclick="delItem('countdowns',${c.id})">🗑</button>
@@ -2310,6 +2369,86 @@ async function deleteAccount(){
   else toast(r.error,'error');
 }
 
+// ── ICAL EXPORT ───────────────────────────────────────────────
+async function getIcalUrl(regen=false){
+  const r=await api('POST', regen?'ical-token/regenerate':'ical-token');
+  if(r.error){toast(r.error,'error');return;}
+  const url=location.origin+'/api/ical/'+r.token+'.ics';
+  document.getElementById('ical-url').value=url;
+  document.getElementById('ical-url-row').style.display='';
+}
+async function regenIcalUrl(){
+  if(!confirm('Neue URL generieren? Der alte Link wird ungültig.'))return;
+  await getIcalUrl(true);
+  toast('Neue iCal-URL generiert');
+}
+function copyIcalUrl(){
+  const input=document.getElementById('ical-url');
+  navigator.clipboard.writeText(input.value).then(()=>toast('URL kopiert ✓')).catch(()=>{input.select();document.execCommand('copy');toast('URL kopiert ✓');});
+}
+
+// ── LOGOUT OTHER DEVICES ──────────────────────────────────────
+async function logoutOther(){
+  if(!confirm('Alle anderen Geräte abmelden?'))return;
+  const r=await api('POST','me/logout-other');
+  if(r.ok) toast('Andere Sitzungen beendet ✓');
+  else toast(r.error,'error');
+}
+
+// ── GRADE CALCULATOR ──────────────────────────────────────────
+let gradeCalcData=[];
+
+function toggleGradeCalc(){
+  const panel=document.getElementById('grade-calc-panel');
+  panel.classList.toggle('open');
+  if(panel.classList.contains('open')) updateGradeCalcSubjects();
+}
+
+function updateGradeCalcSubjects(){
+  const sel=document.getElementById('calc-subject');
+  const subjects=[...new Set(gradeCalcData.map(g=>g.subject).filter(Boolean))].sort();
+  sel.innerHTML='<option value="">Alle Fächer</option>'+subjects.map(s=>`<option value="${esc(s)}">${esc(s)}</option>`).join('');
+  updateGradeCalc();
+}
+
+function updateGradeCalc(){
+  const subj=document.getElementById('calc-subject').value;
+  const type=document.getElementById('calc-type').value;
+  const target=parseFloat(document.getElementById('calc-target').value);
+  const el=document.getElementById('calc-result');
+  if(!el)return;
+
+  const grades=subj?gradeCalcData.filter(g=>g.subject===subj):gradeCalcData;
+  const valid=grades.filter(g=>g.grade!=null);
+  const wSum=valid.reduce((s,g)=>s+(GRADE_WEIGHTS[g.type]||1),0);
+  const wGrades=valid.reduce((s,g)=>s+g.grade*(GRADE_WEIGHTS[g.type]||1),0);
+  const wavg=wSum?wGrades/wSum:null;
+
+  let html='';
+  if(wavg!==null){
+    html+=`<div style="margin-bottom:6px">Aktuell${subj?' ('+esc(subj)+')':''}: <strong style="color:var(--blue)">${wavg.toFixed(2)}</strong> <span style="color:var(--text-muted);font-size:11px">(${valid.length} Note${valid.length!==1?'n':''})</span></div>`;
+  } else {
+    html+=`<div style="margin-bottom:6px;color:var(--text-muted)">Noch keine Noten${subj?' in '+esc(subj):''}.</div>`;
+  }
+
+  if(!isNaN(target)&&target>=1&&target<=6){
+    const w=GRADE_WEIGHTS[type]||1;
+    const needed=((target*(wSum+w))-wGrades)/w;
+    let msg;
+    if(needed<1){
+      msg=`<span style="color:var(--green)">Bereits erreicht – mit ${GRADE_TYPES[type]} egal welche Note.</span>`;
+    } else if(needed>6){
+      msg=`<span style="color:var(--red)">Nicht mehr erreichbar mit einem ${GRADE_TYPES[type]}.</span>`;
+    } else {
+      const col=needed<=2?'var(--green)':needed<=4?'var(--amber)':'var(--red)';
+      msg=`Für Schnitt <strong>${target}</strong> beim nächsten ${GRADE_TYPES[type]}: <strong style="color:${col}">${needed.toFixed(2)}</strong>`;
+    }
+    html+=`<div>${msg}</div>`;
+  }
+
+  el.innerHTML=html;
+}
+
 // ── CHAT ──────────────────────────────────────────────────────
 let chatLastId = 0;
 let chatPollTimer = null;

src/db.js

@@ -248,6 +248,8 @@ try { db.exec(`ALTER TABLE users ADD COLUMN verify_token TEXT`); } catch {}
 try { db.exec(`ALTER TABLE users ADD COLUMN verify_expires TEXT`); } catch {}
 try { db.exec(`ALTER TABLE users ADD COLUMN token_version INTEGER NOT NULL DEFAULT 0`); } catch {}
 try { db.exec(`ALTER TABLE absences ADD COLUMN teacher_id INTEGER`); } catch {}
+try { db.exec(`ALTER TABLE users ADD COLUMN ical_token TEXT`); } catch {}
+try { db.exec(`ALTER TABLE grades ADD COLUMN created_at TEXT DEFAULT (datetime('now'))`); } catch {}
 
 db.exec(`
   CREATE TABLE IF NOT EXISTS password_resets (

src/routes.js

@@ -774,4 +774,131 @@ router.get('/health', (req, res) => {
   }
 });
 
+// --- ICAL EXPORT ---
+const ICAL_BYDAY = { Montag:'MO', Dienstag:'TU', Mittwoch:'WE', Donnerstag:'TH', Freitag:'FR' };
+const ICAL_DAY_OFFSET = { Montag:0, Dienstag:1, Mittwoch:2, Donnerstag:3, Freitag:4 };
+
+function icalDate(s) { return s.replace(/-/g, ''); }
+function icalDateNext(s) {
+  const d = new Date(s); d.setDate(d.getDate() + 1);
+  return d.toISOString().slice(0, 10).replace(/-/g, '');
+}
+function icalEsc(s) {
+  return String(s || '').replace(/\\/g, '\\\\').replace(/,/g, '\\,').replace(/;/g, '\\;').replace(/\n/g, '\\n');
+}
+function icalStamp() {
+  return new Date().toISOString().replace(/[-:]/g, '').slice(0, 15) + 'Z';
+}
+
+router.post('/ical-token', requireAuth, (req, res) => {
+  let { ical_token } = db.prepare('SELECT ical_token FROM users WHERE id = ?').get(req.user.id);
+  if (!ical_token) {
+    ical_token = crypto.randomBytes(24).toString('hex');
+    db.prepare('UPDATE users SET ical_token = ? WHERE id = ?').run(ical_token, req.user.id);
+  }
+  res.json({ token: ical_token });
+});
+
+router.post('/ical-token/regenerate', requireAuth, (req, res) => {
+  const ical_token = crypto.randomBytes(24).toString('hex');
+  db.prepare('UPDATE users SET ical_token = ? WHERE id = ?').run(ical_token, req.user.id);
+  res.json({ token: ical_token });
+});
+
+router.get('/ical/:token.ics', (req, res) => {
+  const row = db.prepare('SELECT id FROM users WHERE ical_token = ?').get(req.params.token);
+  if (!row) return res.status(404).type('text/plain').send('Not found');
+  const uid = row.id;
+  const stamp = icalStamp();
+
+  const timetable   = db.prepare('SELECT * FROM timetable WHERE user_id = ?').all(uid);
+  const homework    = db.prepare("SELECT * FROM homework WHERE user_id = ? AND due_date IS NOT NULL AND done = 0").all(uid);
+  const classEvents = db.prepare('SELECT * FROM class_events WHERE date IS NOT NULL ORDER BY date').all();
+  const countdowns  = db.prepare('SELECT * FROM countdowns WHERE user_id = ?').all(uid);
+
+  const L = [
+    'BEGIN:VCALENDAR',
+    'VERSION:2.0',
+    'PRODID:-//Klassenportal//KP//DE',
+    'CALSCALE:GREGORIAN',
+    'METHOD:PUBLISH',
+    'X-WR-CALNAME:Klassenportal',
+    'X-WR-CALDESC:Stundenplan und Termine',
+  ];
+
+  for (const t of timetable) {
+    const byday = ICAL_BYDAY[t.day];
+    if (!byday) continue;
+    const off = ICAL_DAY_OFFSET[t.day];
+    const base = new Date(2024, 0, 1 + off);
+    const ymd = base.getFullYear().toString() +
+      String(base.getMonth() + 1).padStart(2, '0') +
+      String(base.getDate()).padStart(2, '0');
+    const st = (t.time_start || '08:00').replace(':', '') + '00';
+    const et = (t.time_end   || '08:45').replace(':', '') + '00';
+    const summary = [t.subject, t.room].filter(Boolean).join(' · ');
+    L.push('BEGIN:VEVENT',
+      `UID:tt-${t.id}@klassenportal`,
+      `DTSTAMP:${stamp}`,
+      `DTSTART:${ymd}T${st}`,
+      `DTEND:${ymd}T${et}`,
+      `RRULE:FREQ=WEEKLY;BYDAY=${byday}`,
+      `SUMMARY:${icalEsc(summary || 'Unterricht')}`,
+      ...(t.room    ? [`LOCATION:${icalEsc(t.room)}`]    : []),
+      ...(t.teacher ? [`DESCRIPTION:Lehrer/in: ${icalEsc(t.teacher)}`] : []),
+      'END:VEVENT');
+  }
+
+  for (const h of homework) {
+    const label = h.subject ? `${h.subject}: ${h.title}` : h.title;
+    L.push('BEGIN:VEVENT',
+      `UID:hw-${h.id}@klassenportal`,
+      `DTSTAMP:${stamp}`,
+      `DTSTART;VALUE=DATE:${icalDate(h.due_date)}`,
+      `DTEND;VALUE=DATE:${icalDateNext(h.due_date)}`,
+      `SUMMARY:📚 ${icalEsc(label)}`,
+      'CATEGORIES:Hausaufgaben',
+      'END:VEVENT');
+  }
+
+  const TYPE_ICON = { pruefung:'📝', ferien:'🏖️', termin:'📅', sonstiges:'📌' };
+  for (const e of classEvents) {
+    const icon = TYPE_ICON[e.type] || '📌';
+    const endDate = e.date_end ? icalDateNext(e.date_end) : icalDateNext(e.date);
+    L.push('BEGIN:VEVENT',
+      `UID:ce-${e.id}@klassenportal`,
+      `DTSTAMP:${stamp}`,
+      `DTSTART;VALUE=DATE:${icalDate(e.date)}`,
+      `DTEND;VALUE=DATE:${endDate}`,
+      `SUMMARY:${icon} ${icalEsc(e.title)}`,
+      ...(e.description ? [`DESCRIPTION:${icalEsc(e.description)}`] : []),
+      'END:VEVENT');
+  }
+
+  for (const c of countdowns) {
+    L.push('BEGIN:VEVENT',
+      `UID:cd-${c.id}@klassenportal`,
+      `DTSTAMP:${stamp}`,
+      `DTSTART;VALUE=DATE:${icalDate(c.target_date)}`,
+      `DTEND;VALUE=DATE:${icalDateNext(c.target_date)}`,
+      `SUMMARY:⏳ ${icalEsc(c.title)}`,
+      'END:VEVENT');
+  }
+
+  L.push('END:VCALENDAR');
+
+  res.setHeader('Content-Type', 'text/calendar; charset=utf-8');
+  res.setHeader('Content-Disposition', 'attachment; filename="klassenportal.ics"');
+  res.send(L.join('\r\n'));
+});
+
+// --- SESSION MANAGEMENT ---
+router.post('/me/logout-other', requireAuth, (req, res) => {
+  const newVer = (req.user.token_version | 0) + 1;
+  db.prepare('UPDATE users SET token_version = ? WHERE id = ?').run(newVer, req.user.id);
+  const refreshed = db.prepare('SELECT id, username, role, subject, token_version FROM users WHERE id = ?').get(req.user.id);
+  res.cookie('token', signToken(refreshed), COOKIE_OPTIONS);
+  res.json({ ok: true });
+});
+
 module.exports = router;