Python upgrade + UV for builds #148

We started a python composition function from this template, then gradually derived from it. Some improvements we made were:

• Use uv for the build part, which improved the Docker build phase speed
• Bump python to 3.14, debian-13 as the base image
• Add a Makefile for triggering tests/lint/build
• Bump up the API versions for pkg/metapkg

I wonder if it makes sense to contribute those back to this template.