fix(agent): send Cache-Control: no-store so a new image isn't masked by cache

The control page is a static string served with no cache headers, so after
pulling a fresh agent image the browser kept showing the OLD UI until a hard
refresh (operator-flagged). Add a no-store middleware covering the page and the
status/gpu/logs polls.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ttrj5P7upUTueSfoJcxEqa

agent/fc_agent/app.py

@@ -18,6 +18,17 @@ worker = Worker(cfg)
 app = FastAPI(title="FabledCurator GPU agent")
 
 
+@app.middleware("http")
+async def _no_store(request, call_next):
+    # The control page is a static string and the status/gpu/logs polls are
+    # live data — never let the browser cache either, or a freshly-pulled agent
+    # image still shows the OLD UI until a hard refresh (operator-flagged
+    # 2026-06-30).
+    resp = await call_next(request)
+    resp.headers["Cache-Control"] = "no-store"
+    return resp
+
+
 @app.on_event("startup")
 def _maybe_autostart() -> None:
     # With AUTO_START set, a container restart (host reboot, or `restart: