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_routes.py

@@ -35,6 +35,7 @@ from .handlers.misc_handlers import (
     UsageStatsHandler,
     build_service_registry_adapter,
 )
+from .handlers.base_model_handlers import BaseModelHandlerSet
 from .misc_route_registrar import MiscRouteRegistrar
 
 logger = logging.getLogger(__name__)
@@ -128,6 +129,7 @@ class MiscRoutes:
         custom_words = CustomWordsHandler()
         supporters = SupportersHandler()
         example_workflows = ExampleWorkflowsHandler()
+        base_model = BaseModelHandlerSet()
 
         return self._handler_set_factory(
             health=health,
@@ -143,6 +145,7 @@ class MiscRoutes:
             custom_words=custom_words,
             supporters=supporters,
             example_workflows=example_workflows,
+            base_model=base_model,
         )