feat(ai): add keep-warm ping for chat model

backend/app.py

@@ -41,6 +41,8 @@ AI_K8S_LABEL = os.getenv("AI_K8S_LABEL", "app=ollama")
 AI_K8S_NAMESPACE = os.getenv("AI_K8S_NAMESPACE", "ai")
 AI_MODEL_ANNOTATION = os.getenv("AI_MODEL_ANNOTATION", "ai.bstein.dev/model")
 AI_GPU_ANNOTATION = os.getenv("AI_GPU_ANNOTATION", "ai.bstein.dev/gpu")
+AI_WARM_INTERVAL_SEC = float(os.getenv("AI_WARM_INTERVAL_SEC", "300"))
+AI_WARM_ENABLED = os.getenv("AI_WARM_ENABLED", "true").lower() in ("1", "true", "yes")
 
 _LAB_STATUS_CACHE: dict[str, Any] = {"ts": 0.0, "value": None}
 
@@ -256,6 +258,35 @@ def _discover_ai_meta() -> dict[str, str]:
     return meta
 
 
+def _keep_warm() -> None:
+    """Periodically ping the model to keep it warm."""
+    if not AI_WARM_ENABLED or AI_WARM_INTERVAL_SEC <= 0:
+        return
+
+    def loop() -> None:
+        while True:
+            time.sleep(AI_WARM_INTERVAL_SEC)
+            try:
+                body = {
+                    "model": AI_CHAT_MODEL,
+                    "messages": [{"role": "user", "content": "ping"}],
+                    "stream": False,
+                }
+                with httpx.Client(timeout=min(AI_CHAT_TIMEOUT_SEC, 15)) as client:
+                    client.post(f"{AI_CHAT_API}/api/chat", json=body)
+            except Exception:
+                # best-effort; ignore failures
+                continue
+
+    import threading
+
+    threading.Thread(target=loop, daemon=True, name="ai-keep-warm").start()
+
+
+# Start keep-warm loop on import.
+_keep_warm()
+
+
 @app.route("/", defaults={"path": ""})
 @app.route("/<path:path>")
 def serve_frontend(path: str) -> Any: