safe move + sqlite WAL + log indexes + backup with logs

- fix: imap folder names with spaces (RFC3501 quoting in move/create/select)
- fix: move only deletes source after COPY + Message-ID verification in target
- fix: backup endpoint hung on sqlite write locks — enable WAL + busy_timeout
- perf: indexes on filter_logs(created_at, level, account_id+created_at) for
  fast log queries on millions of rows
- feat: optional "logs mit sichern" checkbox in backup export, restore on import
- UI: backup download uses fetch+blob with error display instead of location.href

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/templates/yaml.html

@@ -9,7 +9,12 @@
     <article>
         <header><h3>Backup erstellen</h3></header>
         <p>Gesamte Konfiguration als JSON-Datei herunterladen.</p>
-        <button onclick="exportBackup()">Backup herunterladen</button>
+        <label style="display:flex; align-items:center; gap:0.5rem; margin-bottom:0.5rem;">
+            <input type="checkbox" id="backup-include-logs" style="margin-bottom:0;">
+            Logs mit sichern <small style="opacity:0.7;">(Datei wird deutlich größer)</small>
+        </label>
+        <button id="backup-download-btn" onclick="exportBackup()">Backup herunterladen</button>
+        <div id="backup-export-status" style="margin-top:0.5rem;"></div>
     </article>
 
     <article>
@@ -47,8 +52,40 @@
 
 {% block scripts %}
 <script>
-function exportBackup() {
-    window.location.href = '/api/yaml/backup';
+async function exportBackup() {
+    const includeLogs = document.getElementById('backup-include-logs').checked;
+    const btn = document.getElementById('backup-download-btn');
+    const statusDiv = document.getElementById('backup-export-status');
+    btn.setAttribute('aria-busy', 'true');
+    btn.disabled = true;
+    statusDiv.innerHTML = `<small>Backup wird erstellt${includeLogs ? ' (Logs werden geladen, kann dauern...)' : ''}</small>`;
+    try {
+        const url = `/api/yaml/backup${includeLogs ? '?include_logs=true' : ''}`;
+        const resp = await fetch(url);
+        if (!resp.ok) {
+            const text = await resp.text().catch(() => '');
+            throw new Error(`HTTP ${resp.status}: ${text || resp.statusText}`);
+        }
+        const blob = await resp.blob();
+        const disposition = resp.headers.get('Content-Disposition') || '';
+        const match = disposition.match(/filename=([^;]+)/);
+        const filename = match ? match[1].trim().replace(/^"|"$/g, '') : 'mailfilter-backup.json';
+        const downloadUrl = URL.createObjectURL(blob);
+        const a = document.createElement('a');
+        a.href = downloadUrl;
+        a.download = filename;
+        document.body.appendChild(a);
+        a.click();
+        a.remove();
+        URL.revokeObjectURL(downloadUrl);
+        const sizeMb = (blob.size / 1024 / 1024).toFixed(2);
+        statusDiv.innerHTML = `<small>Backup heruntergeladen (${sizeMb} MB).</small>`;
+    } catch (e) {
+        statusDiv.innerHTML = `<small style="color:var(--pico-color-red-500, #b00);">Fehler: ${e.message}</small>`;
+    } finally {
+        btn.removeAttribute('aria-busy');
+        btn.disabled = false;
+    }
 }
 
 document.getElementById('backup-import-form').addEventListener('submit', async (e) => {
@@ -67,7 +104,8 @@ document.getElementById('backup-import-form').addEventListener('submit', async (
             Konten erstellt: ${result.accounts_created}<br>
             Konten aktualisiert: ${result.accounts_updated}<br>
             Regeln erstellt: ${result.rules_created}<br>
-            Verarbeitungsstatus: ${result.processed_restored} Einträge
+            Verarbeitungsstatus: ${result.processed_restored} Einträge<br>
+            Logs wiederhergestellt: ${result.logs_restored ?? 0} Einträge
         </article>`;
     }
 });