fix: validate generated keys before creating Serie objects

- Add is_valid_key check in SerieScanner._read_data_from_file() to prevent
  passing invalid keys to Serie constructor (caused ValueError)
- Improve error message for key generation failures
- Add warning log before removing duplicate source folders in rename service

src/core/SerieScanner.py

@@ -24,7 +24,7 @@ from src.config.settings import settings
 from src.core.entities.series import Serie
 from src.core.exceptions.Exceptions import MatchNotFoundError, NoKeyFoundException
 from src.core.providers.base_provider import Loader
-from src.core.utils.key_utils import generate_key_from_folder
+from src.core.utils.key_utils import generate_key_from_folder, is_valid_key
 from src.server.database.connection import get_sync_session
 from src.server.database.service import AnimeSeriesService, EpisodeService
 
@@ -726,6 +726,16 @@ class SerieScanner:
         try:
             generated_key = generate_key_from_folder(folder_name)
             year_from_folder = self._extract_year_from_folder_name(folder_name)
+
+            # Validate that the generated key is usable
+            if not generated_key or not is_valid_key(generated_key):
+                logger.warning(
+                    "Serie key is invalid for folder '%s' (key='%s') - skipping",
+                    folder_name,
+                    generated_key
+                )
+                return None
+
             logger.info(
                 "Generated key for folder '%s' -> key='%s'",
                 folder_name,
@@ -741,7 +751,7 @@ class SerieScanner:
             )
         except Exception as exc:
             logger.warning(
-                "Failed to generate key for folder '%s': %s",
+                "Unexpected error generating key for folder '%s': %s",
                 folder_name,
                 exc
             )

src/server/services/folder_rename_service.py

@@ -602,6 +602,11 @@ async def validate_and_rename_series_folders(dry_run: bool = False) -> Dict[str,
             try:
                 import shutil
 
+                logger.warning(
+                    "Removing source duplicate folder '%s' — target '%s' already exists",
+                    current_name,
+                    expected_name,
+                )
                 shutil.rmtree(series_dir)
                 logger.info(
                     "Removed source folder '%s' — series already exists at target",