fix(server): serve static files with no-cache headers to prevent stale JS/CSS

lightsync/main.py

@@ -1,6 +1,7 @@
 from contextlib import asynccontextmanager
 from pathlib import Path
-from fastapi import FastAPI
+from fastapi import FastAPI, Request
+from fastapi.responses import FileResponse
 from fastapi.staticfiles import StaticFiles
 
 from lightsync.devices.registry import DeviceRegistry
@@ -33,9 +34,17 @@ def create_app() -> FastAPI:
     app.include_router(devices.router, prefix="/api/devices")
     app.include_router(ws.router)
 
-    # Static file serving — MUST be last (catches all unmatched paths)
+    # Static file serving — no-cache headers to prevent stale JS/CSS
     frontend_dir = Path(__file__).parent / "frontend"
-    app.mount("/", StaticFiles(directory=frontend_dir, html=True), name="frontend")
+
+    @app.get("/{filename:path}")
+    async def static_files(request: Request, filename: str):
+        path = frontend_dir / (filename or "index.html")
+        if not path.exists() or not path.is_file():
+            path = frontend_dir / "index.html"
+        response = FileResponse(path)
+        response.headers["Cache-Control"] = "no-cache, no-store, must-revalidate"
+        return response
 
     return app