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/persistent_model_cache.py

@@ -1,13 +1,12 @@
 import json
 import logging
 import os
-import re
 import sqlite3
 import threading
 from dataclasses import dataclass
 from typing import Dict, List, Mapping, Optional, Sequence, Tuple
 
-from ..utils.settings_paths import get_project_root, get_settings_dir
+from ..utils.cache_paths import CacheType, resolve_cache_path_with_migration
 
 logger = logging.getLogger(__name__)
 
@@ -404,20 +403,12 @@ class PersistentModelCache:
     # Internal helpers -------------------------------------------------
 
     def _resolve_default_path(self, library_name: str) -> str:
-        override = os.environ.get("LORA_MANAGER_CACHE_DB")
-        if override:
-            return override
-        try:
-            settings_dir = get_settings_dir(create=True)
-        except Exception as exc:  # pragma: no cover - defensive guard
-            logger.warning("Falling back to project directory for cache: %s", exc)
-            settings_dir = get_project_root()
-        safe_name = re.sub(r"[^A-Za-z0-9_.-]", "_", library_name or "default")
-        if safe_name.lower() in ("default", ""):
-            legacy_path = os.path.join(settings_dir, self._DEFAULT_FILENAME)
-            if os.path.exists(legacy_path):
-                return legacy_path
-        return os.path.join(settings_dir, "model_cache", f"{safe_name}.sqlite")
+        env_override = os.environ.get("LORA_MANAGER_CACHE_DB")
+        return resolve_cache_path_with_migration(
+            CacheType.MODEL,
+            library_name=library_name,
+            env_override=env_override,
+        )
 
     def _initialize_schema(self) -> None:
         with self._db_lock: