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/utils/constants.py

@@ -110,6 +110,8 @@ DIFFUSION_MODEL_BASE_MODELS = frozenset(
         "Wan Video 2.2 T2V-A14B",
         "Wan Video 2.5 T2V",
         "Wan Video 2.5 I2V",
+        "CogVideoX",
+        "Mochi",
         "Qwen",
     ]
 )
@@ -151,6 +153,7 @@ SUPPORTED_DOWNLOAD_SKIP_BASE_MODELS = frozenset(
         "NoobAI",
         "Illustrious",
         "Pony",
+        "Pony V7",
         "HiDream",
         "Qwen",
         "ZImageTurbo",
@@ -158,6 +161,9 @@ SUPPORTED_DOWNLOAD_SKIP_BASE_MODELS = frozenset(
         "SVD",
         "LTXV",
         "LTXV2",
+        "LTXV 2.3",
+        "CogVideoX",
+        "Mochi",
         "Wan Video",
         "Wan Video 1.3B t2v",
         "Wan Video 14B t2v",
@@ -166,6 +172,9 @@ SUPPORTED_DOWNLOAD_SKIP_BASE_MODELS = frozenset(
         "Wan Video 2.2 TI2V-5B",
         "Wan Video 2.2 T2V-A14B",
         "Wan Video 2.2 I2V-A14B",
+        "Wan Video 2.5 T2V",
+        "Wan Video 2.5 I2V",
         "Hunyuan Video",
+        "Anima",
     ]
 )