feat: implement NFO ID storage and media scan tracking

Task 3 (NFO data):
- Add parse_nfo_ids() method to NFOService
- Extract TMDB/TVDB IDs from NFO files during scan
- Update database with extracted IDs
- Add comprehensive unit and integration tests

Task 4 (Media scan):
- Track initial media scan with SystemSettings flag
- Run background loading only on first startup
- Skip media scan on subsequent runs

src/core/services/nfo_service.py

@@ -287,6 +287,87 @@ class NFOService:
             
             return nfo_path
     
+    def parse_nfo_ids(self, nfo_path: Path) -> Dict[str, Optional[int]]:
+        """Parse TMDB ID and TVDB ID from an existing NFO file.
+        
+        Args:
+            nfo_path: Path to tvshow.nfo file
+            
+        Returns:
+            Dictionary with 'tmdb_id' and 'tvdb_id' keys.
+            Values are integers if found, None otherwise.
+            
+        Example:
+            >>> ids = nfo_service.parse_nfo_ids(Path("/anime/series/tvshow.nfo"))
+            >>> print(ids)
+            {'tmdb_id': 1429, 'tvdb_id': 79168}
+        """
+        result = {"tmdb_id": None, "tvdb_id": None}
+        
+        if not nfo_path.exists():
+            logger.debug(f"NFO file not found: {nfo_path}")
+            return result
+        
+        try:
+            tree = etree.parse(str(nfo_path))
+            root = tree.getroot()
+            
+            # Try to find TMDB ID from uniqueid elements first
+            for uniqueid in root.findall(".//uniqueid"):
+                uid_type = uniqueid.get("type")
+                uid_text = uniqueid.text
+                
+                if uid_type == "tmdb" and uid_text:
+                    try:
+                        result["tmdb_id"] = int(uid_text)
+                    except ValueError:
+                        logger.warning(
+                            f"Invalid TMDB ID format in NFO: {uid_text}"
+                        )
+                
+                elif uid_type == "tvdb" and uid_text:
+                    try:
+                        result["tvdb_id"] = int(uid_text)
+                    except ValueError:
+                        logger.warning(
+                            f"Invalid TVDB ID format in NFO: {uid_text}"
+                        )
+            
+            # Fallback: check for dedicated tmdbid/tvdbid elements
+            if result["tmdb_id"] is None:
+                tmdbid_elem = root.find(".//tmdbid")
+                if tmdbid_elem is not None and tmdbid_elem.text:
+                    try:
+                        result["tmdb_id"] = int(tmdbid_elem.text)
+                    except ValueError:
+                        logger.warning(
+                            f"Invalid TMDB ID format in tmdbid element: "
+                            f"{tmdbid_elem.text}"
+                        )
+            
+            if result["tvdb_id"] is None:
+                tvdbid_elem = root.find(".//tvdbid")
+                if tvdbid_elem is not None and tvdbid_elem.text:
+                    try:
+                        result["tvdb_id"] = int(tvdbid_elem.text)
+                    except ValueError:
+                        logger.warning(
+                            f"Invalid TVDB ID format in tvdbid element: "
+                            f"{tvdbid_elem.text}"
+                        )
+            
+            logger.debug(
+                f"Parsed IDs from NFO: {nfo_path.name} - "
+                f"TMDB: {result['tmdb_id']}, TVDB: {result['tvdb_id']}"
+            )
+            
+        except etree.XMLSyntaxError as e:
+            logger.error(f"Invalid XML in NFO file {nfo_path}: {e}")
+        except Exception as e:  # pylint: disable=broad-except
+            logger.error(f"Error parsing NFO file {nfo_path}: {e}")
+        
+        return result
+    
     def _find_best_match(
         self,
         results: List[Dict[str, Any]],