refactor(cache): reorganize cache directory structure with automatic legacy cleanup

- Centralize cache path resolution in new py/utils/cache_paths.py module
- Migrate legacy cache files to organized structure: {settings_dir}/cache/{model|recipe|fts|symlink}/
- Automatically clean up legacy files after successful migration with integrity verification
- Update Config symlink cache to use new path and migrate from old location
- Simplify service classes (PersistentModelCache, PersistentRecipeCache, RecipeFTSIndex, TagFTSIndex) to use centralized migration logic
- Add comprehensive test coverage for cache paths and automatic cleanup

py/services/recipe_fts_index.py

@@ -15,7 +15,7 @@ import threading
 import time
 from typing import Any, Dict, List, Optional, Set
 
-from ..utils.settings_paths import get_settings_dir
+from ..utils.cache_paths import CacheType, resolve_cache_path_with_migration
 
 logger = logging.getLogger(__name__)
 
@@ -67,17 +67,11 @@ class RecipeFTSIndex:
 
     def _resolve_default_path(self) -> str:
         """Resolve the default database path."""
-        override = os.environ.get("LORA_MANAGER_RECIPE_FTS_DB")
-        if override:
-            return override
-
-        try:
-            settings_dir = get_settings_dir(create=True)
-        except Exception as exc:
-            logger.warning("Falling back to current directory for FTS index: %s", exc)
-            settings_dir = "."
-
-        return os.path.join(settings_dir, self._DEFAULT_FILENAME)
+        env_override = os.environ.get("LORA_MANAGER_RECIPE_FTS_DB")
+        return resolve_cache_path_with_migration(
+            CacheType.RECIPE_FTS,
+            env_override=env_override,
+        )
 
     def get_database_path(self) -> str:
         """Return the resolved database path."""