Automatische DB-Backups: nächtlich, gzip, Rotation, optional Discord-Upload

- SQLite-Online-Backup (WAL-sicher) täglich 03:00 → data/backups/*.db.gz, 14 Tage Rotation
- Optional Offsite-Kopie als Upload in einen privaten Discord-Kanal (Setting)
- Setup-Seite: Toggle, Upload-Kanal, 'Backup jetzt'-Button; letztes Backup im Status-Panel

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/pages/Settings.jsx

@@ -134,6 +134,10 @@ export default function Settings({ me }) {
                         <div className="stat"><span className="stat-value">{data.status.devlogs}</span><span className="stat-label">Devlogs</span></div>
                         <div className="stat"><span className="stat-value">{data.status.commits}</span><span className="stat-label">Commits</span></div>
                         <div className="stat"><span className="stat-value">{fmtBytes(data.status.dbSizeBytes)}</span><span className="stat-label">Datenbank</span></div>
+                        <div className="stat">
+                            <span className="stat-value">{data.status.lastBackup ? data.status.lastBackup.slice(0, 10) : '—'}</span>
+                            <span className="stat-label">Letztes Backup</span>
+                        </div>
                     </div>
                 </div>
 
@@ -282,6 +286,35 @@ export default function Settings({ me }) {
                     </div>
                 </div>
 
+                {/* Backups */}
+                <div className="settings-section">
+                    <h2 className="settings-title">// Backups</h2>
+                    <div className="field">
+                        <label className="toggle">
+                            <input
+                                type="checkbox"
+                                checked={form.backup_enabled}
+                                onChange={(e) => setForm({ ...form, backup_enabled: e.target.checked })}
+                            />
+                            <span>Nächtliches DB-Backup (03:00)</span>
+                            <span className="field-hint">gzip nach data/backups/, 14 Tage Rotation</span>
+                        </label>
+                    </div>
+                    <div className="field">
+                        <label>Upload-Kanal <span className="field-hint">Offsite-Kopie in einen PRIVATEN Kanal — leer = nur lokal</span></label>
+                        <div className="field-row">
+                            <select
+                                value={form.backup_channel_id ?? ''}
+                                onChange={(e) => setForm({ ...form, backup_channel_id: e.target.value })}
+                            >
+                                <option value="">— nur lokal —</option>
+                                {channelOptions}
+                            </select>
+                            <button className="btn" onClick={() => sendTest('backup')}>Backup jetzt</button>
+                        </div>
+                    </div>
+                </div>
+
                 {/* API-Keys */}
                 <div className="settings-section">
                     <h2 className="settings-title">// API-Keys (/api/v1)</h2>