automatic DB maintenance: log rotation, orphan cleanup, VACUUM

The existing daily cleanup never effectively ran: it was an interval
job counted from container start (reset on every deploy), it called
asyncio.get_event_loop() from a worker thread, and even when deleting,
SQLite never returns freed pages to the filesystem. Live DB: 4.1 GB,
of which 2.6 GB log and 0.6 GB unused pages.

New maintenance service, scheduled daily at MAINTENANCE_HOUR_UTC:30
and once 5 minutes after every start:
- delete log entries older than LOG_RETENTION_DAYS (30) and keep at
  most LOG_MAX_ENTRIES (200k) newest ones
- delete processed_mails markers of deleted rules/accounts (FKs are
  not enforced by SQLite)
- VACUUM when >25% of the file is unused, only if free disk space
  covers the copy; never runs twice in parallel

GET/POST /api/logs/maintenance expose status and a manual run; the log
menu shows DB size, entry count and last run, with "Datenbank
aufräumen & verkleinern". Removed the dead cleanup_old_logs.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/routers/logs.py

@@ -7,6 +7,7 @@ from sqlalchemy.orm import Session
 
 from app.database import engine, get_db
 from app.models.db_models import FilterLog, LogLevel
+from app.services.maintenance import db_status, run_maintenance
 
 logger = logging.getLogger(__name__)
 
@@ -134,6 +135,23 @@ def get_logs(
     }
 
 
+@router.get("/maintenance")
+def maintenance_status():
+    """Größe der Datenbank, Anzahl Einträge und Ergebnis der letzten Wartung."""
+    return db_status()
+
+
+@router.post("/maintenance")
+def maintenance_run(vacuum: bool = False):
+    """Wartung sofort ausführen (Log-Rotation, verwaiste Marker, ggf. VACUUM).
+    vacuum=true erzwingt das Verkleinern der Datei."""
+    try:
+        result = run_maintenance(force_vacuum=vacuum)
+    except Exception as e:
+        raise HTTPException(500, f"Wartung fehlgeschlagen: {e}")
+    return {"result": result, "status": db_status()}
+
+
 @router.delete("/")
 def clear_logs(account_id: int | None = None, db: Session = Depends(get_db)):
     """Löscht Logs. Ohne account_id: schnelles Drop+Recreate der Tabelle