feat: implement timezone-aware logging system

- Fix inconsistent timestamp formats in logs for easier troubleshooting
- All logging systems now respect Docker TZ environment variable (e.g., TZ=America/New_York)
- Add TimezoneAwareFormatter for Python's standard logging module
- Enhance _log function with robust timezone support and fallbacks
- Replace placeholder logging functions with centralized core.logging._log
- Support both zoneinfo (Python 3.9+) and pytz (older versions)
- Users now see consistent timezone formatting across all log outputs

core/logging.py

@@ -1,7 +1,29 @@
 """Logging utilities for NFOguard"""
 
 from datetime import datetime, timezone
+import os
+
+def _get_local_timezone():
+    """Get the local timezone, respecting TZ environment variable"""
+    tz_name = os.environ.get('TZ', 'UTC')
+    
+    try:
+        # Try zoneinfo first (Python 3.9+)
+        from zoneinfo import ZoneInfo
+        return ZoneInfo(tz_name)
+    except ImportError:
+        # Fallback for older Python versions
+        try:
+            import pytz
+            return pytz.timezone(tz_name)
+        except:
+            # Final fallback to UTC
+            return timezone.utc
+    except:
+        # If zone name is invalid, fallback to UTC
+        return timezone.utc
 
 def _log(level: str, msg: str):
     """Basic logging function that writes to console"""
-    print(f"[{datetime.now(timezone.utc).isoformat(timespec='seconds')}] {level}: {msg}")
+    tz = _get_local_timezone()
+    print(f"[{datetime.now(tz).isoformat(timespec='seconds')}] {level}: {msg}")