Fix: UTC fuer interne Timer, Berlin nur fuer Anzeige

Korrektur: Alle DB-Timestamps (refresh_log, created_at, updated_at,
auth, notifications) bleiben UTC fuer korrekte Timer-Vergleiche.
Europe/Berlin nur fuer angezeigte Werte (Exporte, Prompts, API).
Verhindert zu fruehes Ausloesen des Auto-Refresh-Timers.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/main.py

@@ -5,7 +5,7 @@ import logging
 import os
 import sys
 from contextlib import asynccontextmanager
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Dict
 
 from fastapi import FastAPI, WebSocket, WebSocketDisconnect, Depends, Request, Response
@@ -93,7 +93,7 @@ async def check_auto_refresh():
         )
         incidents = await cursor.fetchall()
 
-        now = datetime.now(TIMEZONE)
+        now = datetime.now(timezone.utc)
 
         for incident in incidents:
             incident_id = incident["id"]
@@ -112,7 +112,7 @@ async def check_auto_refresh():
             else:
                 last_time = datetime.fromisoformat(last_refresh["completed_at"])
                 if last_time.tzinfo is None:
-                    last_time = last_time.replace(tzinfo=TIMEZONE)
+                    last_time = last_time.replace(tzinfo=timezone.utc)
                 elapsed = (now - last_time).total_seconds() / 60
                 if elapsed >= interval:
                     should_refresh = True
@@ -143,11 +143,11 @@ async def cleanup_expired():
         )
         incidents = await cursor.fetchall()
 
-        now = datetime.now(TIMEZONE)
+        now = datetime.now(timezone.utc)
         for incident in incidents:
             created = datetime.fromisoformat(incident["created_at"])
             if created.tzinfo is None:
-                created = created.replace(tzinfo=TIMEZONE)
+                created = created.replace(tzinfo=timezone.utc)
             age_days = (now - created).days
             if age_days >= incident["retention_days"]:
                 await db.execute(
@@ -164,7 +164,7 @@ async def cleanup_expired():
         for orphan in orphans:
             started = datetime.fromisoformat(orphan["started_at"])
             if started.tzinfo is None:
-                started = started.replace(tzinfo=TIMEZONE)
+                started = started.replace(tzinfo=timezone.utc)
             age_minutes = (now - started).total_seconds() / 60
             if age_minutes >= 15:
                 await db.execute(
@@ -195,7 +195,7 @@ async def lifespan(app: FastAPI):
     try:
         result = await db.execute(
             "UPDATE refresh_log SET status = 'error', completed_at = ?, error_message = 'Verwaist (Neustart, automatisch bereinigt)' WHERE status = 'running'",
-            (datetime.now(TIMEZONE).isoformat(),),
+            (datetime.now(timezone.utc).strftime('%Y-%m-%d %H:%M:%S'),),
         )
         if result.rowcount > 0:
             await db.commit()