feat: enhance model caching and output modalities handling

- Updated `refresh_models_cache` to include output modalities in the models cache.
- Added `get_model_output_modalities` function to retrieve output modalities for a specific model.
- Modified tests to cover new functionality for output modalities.
- Updated OpenRouter video generation functions to support audio generation and improved error handling.
- Enhanced dashboard to display generated images and videos.
- Refactored frontend templates to accommodate new data structures for generated content.
- Adjusted tests to validate changes in model handling and dashboard rendering.

Co-authored-by: Copilot <copilot@github.com>

backend/app/models/ai.py

@@ -62,6 +62,7 @@ class ImageResult(BaseModel):
     url: str | None = None
     b64_json: str | None = None
     revised_prompt: str | None = None
+    image_id: str | None = None  # UUID of stored row in generated_images
 
 
 class ImageResponse(BaseModel):