Add models caching and management functionality with corresponding API endpoints and templates

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

backend/app/routers/models.py

@@ -0,0 +1,47 @@
+"""Models router: list and refresh the OpenRouter model cache."""
+from fastapi import APIRouter, Depends, HTTPException, Query, status
+
+from ..db import get_conn, get_write_lock
+from ..dependencies import get_current_user, require_admin
+from ..services import models as models_service
+
+router = APIRouter(prefix="/models", tags=["models"])
+
+
+@router.get("/")
+async def list_models(
+    modality: str | None = Query(
+        None,
+        description="Filter by output modality: text, image, video, audio",
+    ),
+    _: dict = Depends(get_current_user),
+):
+    """Return cached models. Auto-refreshes cache if stale (older than 24 h)."""
+    conn = get_conn()
+    if models_service.is_cache_stale(conn):
+        async with get_write_lock():
+            # Re-check inside lock to avoid redundant parallel refreshes
+            if models_service.is_cache_stale(conn):
+                try:
+                    await models_service.refresh_models_cache(conn)
+                except Exception as exc:
+                    raise HTTPException(
+                        status_code=status.HTTP_502_BAD_GATEWAY,
+                        detail=f"Failed to refresh model cache: {exc}",
+                    )
+    return models_service.get_cached_models(conn, modality)
+
+
+@router.post("/refresh", status_code=200)
+async def refresh_models(_: dict = Depends(require_admin)):
+    """Force-refresh the model cache from OpenRouter. Admin only."""
+    conn = get_conn()
+    async with get_write_lock():
+        try:
+            count = await models_service.refresh_models_cache(conn)
+        except Exception as exc:
+            raise HTTPException(
+                status_code=status.HTTP_502_BAD_GATEWAY,
+                detail=f"OpenRouter error: {exc}",
+            )
+    return {"refreshed": count}