Migrate the backend from pip to uv

Replace requirements.txt with a uv workspace and lockfile, install the five tavolo packages from packages/* in development and non-editable in the image, and build the Docker image with uv. Move dev tools to a PEP 735 dependency group and refresh the locked dependency versions.

server/packages/tavolo-app/README.md

@@ -29,7 +29,7 @@ The deployable tavolo application: the composition root wiring
 ## Development (from `packages/tavolo-app/`)
 
 ```sh
-.venv/bin/python -m mypy --namespace-packages --explicit-package-bases \
+uv run mypy --namespace-packages --explicit-package-bases \
   src/tavolo/app.py \
   src/tavolo/config.py \
   src/tavolo/telemetry.py \