fix(frontend): no-cache Header für Static-Files und Index

Browser haben nach Deploys die alten app.js / style.css aus dem Cache
weiterbenutzt. Mit Cache-Control: no-cache, must-revalidate wird bei
jeder Anfrage revalidiert (304 wenn unverändert, 200 wenn neu).

lxc-frontend/app/main.py

@@ -5,12 +5,22 @@ from pathlib import Path
 from fastapi import FastAPI
 from fastapi.responses import FileResponse, JSONResponse
 from fastapi.staticfiles import StaticFiles
+from starlette.types import Scope
 
 from app.api.jobs import router as jobs_router
 from app.core.config import settings
 from app.core.db import init_db
 from app.core.mac_client import MacClient
 
+
+class NoCacheStaticFiles(StaticFiles):
+    """StaticFiles, die Browser zu Revalidierung zwingen (verhindert hängende Caches nach Deploy)."""
+
+    async def get_response(self, path: str, scope: Scope):
+        response = await super().get_response(path, scope)
+        response.headers["Cache-Control"] = "no-cache, must-revalidate"
+        return response
+
 logging.basicConfig(level=logging.INFO, format="%(asctime)s [%(levelname)s] %(name)s: %(message)s")
 log = logging.getLogger("voice-agent")
 
@@ -29,12 +39,12 @@ app = FastAPI(title=settings.app_name, lifespan=lifespan)
 app.include_router(jobs_router)
 
 STATIC_DIR = Path(__file__).resolve().parent / "static"
-app.mount("/static", StaticFiles(directory=STATIC_DIR), name="static")
+app.mount("/static", NoCacheStaticFiles(directory=STATIC_DIR), name="static")
 
 
 @app.get("/")
 def index():
-    return FileResponse(STATIC_DIR / "index.html")
+    return FileResponse(STATIC_DIR / "index.html", headers={"Cache-Control": "no-cache, must-revalidate"})
 
 
 @app.get("/health")