feat: email verification via Resend + admin user management

- Add email verification flow: register sends verify link, login blocks unverified accounts, 24h token expiry, resend endpoint (3/h rate limit).
- Add mailer module using Resend with branded HTML + plaintext template.
- Extend admin dashboard: verified-status column, toggle verify/unverify buttons, promote/demote admin role, delete any non-self user.
- Migrate users table: email_verified, verify_token, verify_expires columns.
- Load env via dotenv; add .env to gitignore.

index.js

@@ -1,3 +1,4 @@
+require('dotenv').config();
 const express = require('express');
 const cookieParser = require('cookie-parser');
 const helmet = require('helmet');
@@ -41,6 +42,7 @@ const html = f => (req, res) => res.sendFile(path.join(__dirname, 'public', f));
 app.get('/login', html('login.html'));
 app.get('/admin', html('admin.html'));
 app.get('/datenschutz', html('datenschutz.html'));
+app.get('/app', html('app.html'));
 app.get('/{*path}', html('index.html'));
 
 app.listen(PORT, '127.0.0.1', () => console.log(`info1 läuft auf :${PORT}`));