Fix control SPA refresh 404 on /stats by serving index.html.

Co-authored-by: Cursor <cursoragent@cursor.com>

control/backend/app/main.py

@@ -59,16 +59,15 @@ if (_DIST / "assets").is_dir():
 
 @app.get("/")
 @app.get("/monitor")
+@app.get("/stats")
 @app.get("/settings")
 @app.get("/login")
-async def spa(full_path: str = ""):
+async def spa():
     index = _DIST / "index.html"
     if index.exists():
         return FileResponse(index)
-    if Path(__file__).name:
-        return {
-            "ok": True,
-            "msg": "control frontend not built; cd control/frontend && npm ci && npm run build",
-            "health": "/health",
-        }
-    raise HTTPException(status_code=404, detail="frontend missing")
+    return {
+        "ok": True,
+        "msg": "control frontend not built; cd control/frontend && npm ci && npm run build",
+        "health": "/health",
+    }