Add opt-in model update endpoint + API key support

Gateway: POST /admin/update-model downloads new GGUF and reloads.
Disabled by default — requires ALLOW_MODEL_UPDATES=true in .env.
Matt controls whether remote model updates are allowed.

Self-play: --api-key flag for authenticated gateway connections.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

gateway.py

@@ -252,8 +252,50 @@ class GatewayHandler(BaseHTTPRequestHandler):
         length = int(self.headers.get("Content-Length", 0))
         body = json.loads(self.rfile.read(length)) if length > 0 else None
 
+        # Model update endpoint — downloads new GGUF and reloads
+        if self.path == "/admin/update-model" and body:
+            self._handle_model_update(body)
+            return
+
         self._proxy_to_ollama(self.path, body)
 
+    def _handle_model_update(self, body):
+        """Download a new GGUF from a URL and reload the model.
+        Request: {"url": "https://mortdec.ai/dl/...", "name": "mortdecai-v5"}
+        This is opt-in — the gateway operator must enable ALLOW_MODEL_UPDATES=true.
+        """
+        if os.environ.get("ALLOW_MODEL_UPDATES", "false").lower() != "true":
+            self._send_json(403, {"error": "Model updates disabled. Set ALLOW_MODEL_UPDATES=true in .env to enable."})
+            return
+
+        url = body.get("url")
+        name = body.get("name", "mortdecai-latest")
+        if not url:
+            self._send_json(400, {"error": "url is required"})
+            return
+
+        try:
+            import subprocess
+
+            # Download GGUF
+            gguf_path = f"/models/{name}.gguf"
+            print(f"Downloading model from {url}...")
+            r = requests.get(url, stream=True, timeout=600)
+            r.raise_for_status()
+            with open(f"models/{name}.gguf", "wb") as f:
+                for chunk in r.iter_content(chunk_size=8192):
+                    f.write(chunk)
+
+            # Create Modelfile and load
+            subprocess.run(
+                ["docker", "exec", "mortdecai-ollama", "ollama", "create", name, "-f", f"/models/Modelfile"],
+                timeout=120, check=True
+            )
+
+            self._send_json(200, {"status": "ok", "model": name, "message": "Model updated and loaded"})
+        except Exception as e:
+            self._send_json(500, {"error": f"Update failed: {e}"})
+
     def _serve_dashboard(self):
         """Simple HTML dashboard showing usage stats."""
         with _stats_lock: