Validate AVConnect credentials on saving. Improved AVConnect login method. Fixed issue with UTC datetimes

src/core/config.py

@@ -1,7 +1,19 @@
 import logging
 import os
+from datetime import datetime, timezone
 from typing import Optional
 
+
+def utcnow() -> datetime:
+    """Return the current UTC time as a timezone-naive datetime.
+
+    SQLite (and SQLAlchemy's default column handling) stores datetimes without
+    timezone info. Using this helper keeps all DB timestamps and comparisons
+    consistent and avoids TypeError on offset-naive vs offset-aware comparisons.
+    """
+    return datetime.now(timezone.utc).replace(tzinfo=None)
+
+
 # ── Paths ─────────────────────────────────────────────────────────────────────
 _HERE = os.path.dirname(os.path.abspath(__file__))   # src/core/
 _SRC_DIR = os.path.dirname(_HERE)                    # src/