perf(api,frontend): index hot queries, paginate chats, fix realtime

backend/src/api/app.py

@@ -34,6 +34,7 @@ from api.routers import (
     watches,
 )
 from dependencies.container import container
+from utils.cache import DAY_HEADERS, IMMUTABLE_HEADERS, NO_STORE_HEADERS
 from utils.env import env
 
 if env.auth.token is None:
@@ -105,8 +106,11 @@ if _spa_dir.is_dir():
     async def serve_spa(spa_path: str) -> FileResponse:
         candidate = (_spa_dir / spa_path).resolve()
         if spa_path and candidate.is_relative_to(_spa_dir) and candidate.is_file():
-            return FileResponse(candidate)
-        return FileResponse(_spa_index)
+            immutable = spa_path.startswith("_app/immutable/")
+            return FileResponse(
+                candidate, headers=IMMUTABLE_HEADERS if immutable else DAY_HEADERS
+            )
+        return FileResponse(_spa_index, headers=NO_STORE_HEADERS)
 
 
 app.add_middleware(BearerAuthMiddleware, token=_token)