feat: Dynamic base model fetching from Civitai API (#854)

Implement automatic fetching of base models from Civitai API to keep
data up-to-date without manual updates.

Backend:
- Add CivitaiBaseModelService with 7-day TTL caching
- Add /api/lm/base-models endpoints for fetching and refreshing
- Merge hardcoded and remote models for backward compatibility
- Smart abbreviation generation for unknown models

Frontend:
- Add civitaiBaseModelApi client for API communication
- Dynamic base model loading on app initialization
- Update SettingsManager to use merged model lists
- Add support for 8 new models: Anima, CogVideoX, LTXV 2.3, Mochi,
  Pony V7, Wan Video 2.5 T2V/I2V

API Endpoints:
- GET /api/lm/base-models - Get merged models
- POST /api/lm/base-models/refresh - Force refresh
- GET /api/lm/base-models/categories - Get categories
- GET /api/lm/base-models/cache-status - Check cache status

Closes #854

py/routes/misc_route_registrar.py

@@ -56,6 +56,15 @@ MISC_ROUTE_DEFINITIONS: tuple[RouteDefinition, ...] = (
     RouteDefinition(
         "GET", "/api/lm/example-workflows/{filename}", "get_example_workflow"
     ),
+    # Base model management routes
+    RouteDefinition("GET", "/api/lm/base-models", "get_base_models"),
+    RouteDefinition("POST", "/api/lm/base-models/refresh", "refresh_base_models"),
+    RouteDefinition(
+        "GET", "/api/lm/base-models/categories", "get_base_model_categories"
+    ),
+    RouteDefinition(
+        "GET", "/api/lm/base-models/cache-status", "get_base_model_cache_status"
+    ),
 )