CRITICAL: Fix database upsert bug preventing manual scan date persistence

**Root Cause**: upsert_movie_dates() was UPDATE-only, not proper upsert
- Manual scans failed to save dateadded to database (NULL values)
- Webhooks found database entries but with NULL dateadded
- Fell back to current timestamp instead of using proper import dates

**Database Fix**:
- Changed core/database.py upsert_movie_dates() from UPDATE to INSERT OR REPLACE
- Now properly saves dateadded during manual scans
- Preserves existing path with COALESCE fallback

**Webhook Enhancement**:
- Added comprehensive debug logging for database lookups
- Enhanced webhook date decision logic with proper fallback chain
- Only uses current timestamp as absolute last resort

**Impact**:
- Movies: Manual scans now persist dates, webhooks find existing entries ✅
- TV Shows: Not affected - already using proper INSERT OR REPLACE ✅
- Version: 1.5.5

core/database.py

@@ -175,11 +175,15 @@ class NFOGuardDatabase:
         """Insert or update movie date record"""
         with self.get_connection() as conn:
             cursor = conn.cursor()
+            # Use INSERT OR REPLACE to ensure we always update the dates properly
             cursor.execute("""
-                UPDATE movies 
-                SET released = ?, dateadded = ?, source = ?, has_video_file = ?, last_updated = ?
-                WHERE imdb_id = ?
-            """, (released, dateadded, source, has_video_file, datetime.utcnow().isoformat(), imdb_id))
+                INSERT OR REPLACE INTO movies (imdb_id, path, released, dateadded, source, has_video_file, last_updated)
+                VALUES (
+                    ?, 
+                    COALESCE((SELECT path FROM movies WHERE imdb_id = ?), 'unknown'),
+                    ?, ?, ?, ?, ?
+                )
+            """, (imdb_id, imdb_id, released, dateadded, source, has_video_file, datetime.utcnow().isoformat()))
     
     def get_series_episodes(self, imdb_id: str, has_video_file_only: bool = False) -> List[Dict]:
         """Get all episodes for a series"""