add zip; track current Ubuntu python via unversioned meta packages

Bumped to python3 / python3-venv (no minor pin). FROM ubuntu rolled
forward to resolute (25.10), which dropped python3.12 and broke the
1.1.3 build. Unversioned packages track whatever ships in the current
release.

Author: ClaydeCode

Dockerfile

@@ -2,8 +2,8 @@ FROM ubuntu
 
 RUN apt-get update && apt-get install -y \
     curl \
-    python3.12 \
-    python3.12-venv \
+    python3 \
+    python3-venv \
     python3-pip \
     docker-compose-v2 \
     zip