deploy/mainnet/chatmock: healthcheck via urllib (wget absent in image)

The storagetime/chatmock image has neither wget nor curl, so the
previous wget-based healthcheck always failed with "executable file
not found" and the container sat in "starting" forever. The image
does carry a Python interpreter (chatmock is a Flask app), so swap
to a 1-liner urllib probe of /health. /health returns 200 even
before OAuth login, so a red healthcheck now means the Flask server
itself is down.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

deploy/mainnet/docker-compose.chatmock.yml

@@ -53,7 +53,10 @@ services:
     volumes:
       - chatmock_data:/data
     healthcheck:
-      test: ["CMD-SHELL", "wget -qO- http://localhost:8000/health >/dev/null || exit 1"]
+      # chatmock image has neither curl nor wget — use the bundled Python's
+      # urllib to probe /health. /health returns 200 even before OAuth login
+      # so an unhealthy state here means the Flask server itself is down.
+      test: ["CMD-SHELL", "python3 -c 'import urllib.request,sys; sys.exit(0 if urllib.request.urlopen(\"http://localhost:8000/health\", timeout=3).status==200 else 1)' || exit 1"]
       interval: 20s
       timeout: 5s
       retries: 3