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/db.py

@@ -86,6 +86,34 @@ def _run_migrations(conn: duckdb.DuckDBPyConnection) -> None:
             fetched_at     TIMESTAMP NOT NULL
         )
     """)
+    conn.execute("""
+        CREATE TABLE IF NOT EXISTS generated_images (
+            id          UUID      DEFAULT uuid() PRIMARY KEY,
+            user_id     UUID      NOT NULL,
+            model_id    VARCHAR   NOT NULL,
+            prompt      VARCHAR   NOT NULL,
+            image_data  VARCHAR   NOT NULL,
+            created_at  TIMESTAMP DEFAULT now()
+        )
+    """)
+    conn.execute("""
+        CREATE TABLE IF NOT EXISTS generated_videos (
+            id          UUID      DEFAULT uuid() PRIMARY KEY,
+            user_id     UUID      NOT NULL,
+            job_id      VARCHAR   NOT NULL,
+            model_id    VARCHAR   NOT NULL,
+            prompt      VARCHAR   NOT NULL,
+            polling_url VARCHAR,
+            status      VARCHAR   NOT NULL DEFAULT 'pending',
+            video_url   VARCHAR,
+            created_at  TIMESTAMP DEFAULT now(),
+            updated_at  TIMESTAMP DEFAULT now()
+        )
+    """)
+    # Migration: add output_modalities column if absent (stores JSON array string)
+    conn.execute("""
+        ALTER TABLE models_cache ADD COLUMN IF NOT EXISTS output_modalities VARCHAR
+    """)
     _seed_admin(conn)