feat: Add dedicated failed movies debug log

- Create logs/failed_movies.log for movies with no_valid_date_source
- Logs movie name, IMDb ID, failure reason, and timestamp
- Helps users identify problematic movies needing manual attention
- Useful for debugging API issues and monitoring system health
- Documented in SUMMARY.md action items for troubleshooting workflow

nfoguard.py

@@ -1281,6 +1281,10 @@ class MovieProcessor:
             return self._get_file_mtime_date(movie_path)
         else:
             _log("INFO", f"No valid dates found for {imdb_id} and file date fallback disabled - skipping NFO creation")
+            
+            # Log to failed movies debug file for troubleshooting
+            self._log_failed_movie(movie_path, imdb_id, "No import date, no release date, file date fallback disabled")
+            
             return None, "no_valid_date_source", None
     
     def _get_digital_release_date(self, imdb_id: str) -> Tuple[Optional[str], str]:
@@ -1334,6 +1338,28 @@ class MovieProcessor:
             _log("ERROR", f"Error reading Radarr NFO file: {e}")
             return None
     
+    def _log_failed_movie(self, movie_path: Path, imdb_id: str, reason: str, available_countries: List[str] = None):
+        """Log movies that failed to get valid dates to a debug file"""
+        try:
+            log_dir = Path("logs")
+            log_dir.mkdir(exist_ok=True)
+            
+            failed_log_path = log_dir / "failed_movies.log"
+            timestamp = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
+            
+            log_entry = f"[{timestamp}] {movie_path.name} | IMDb: {imdb_id} | Reason: {reason}"
+            if available_countries:
+                log_entry += f" | Available Countries: {', '.join(available_countries)}"
+            log_entry += "\n"
+            
+            with open(failed_log_path, "a", encoding="utf-8") as f:
+                f.write(log_entry)
+            
+            _log("INFO", f"📝 Logged failed movie to {failed_log_path}: {movie_path.name}")
+            
+        except Exception as e:
+            _log("ERROR", f"Failed to write to failed movies log: {e}")
+    
     def _get_file_mtime_date(self, movie_path: Path) -> Tuple[str, str, Optional[str]]:
         """Get date from file modification time as last resort"""
         video_exts = (".mkv", ".mp4", ".avi", ".mov", ".m4v")