feat(frontend): add static file serving for production build

backend/app/main.py

@@ -1,6 +1,8 @@
 import os
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
+from fastapi.staticfiles import StaticFiles
+from fastapi.responses import FileResponse
 from contextlib import asynccontextmanager
 from app.database import engine, Base
 from app import models  # noqa: F401 - registers models with Base.metadata
@@ -40,3 +42,15 @@ app.include_router(dashboard.router)
 @app.get("/api/health")
 async def health_check():
     return {"status": "healthy"}
+
+# Static files for production
+frontend_dist = os.path.join(os.path.dirname(__file__), "../../frontend/dist")
+if os.path.exists(frontend_dist):
+    app.mount("/assets", StaticFiles(directory=os.path.join(frontend_dist, "assets")), name="assets")
+
+    @app.get("/{path:path}")
+    async def serve_frontend(path: str):
+        index_file = os.path.join(frontend_dist, "index.html")
+        if os.path.exists(index_file):
+            return FileResponse(index_file)
+        return {"detail": "Frontend not built"}