Use --frozen option in aliases

This helps to avoid updating `uv.lock` and to preserve the consistency
of the development environment.

Author: tomschr

changelog.d/+alias.infra.rst

@@ -0,0 +1,2 @@
+Use ``--frozen`` option in aliases to avoid updating :filename:`uv.lock`.
+Add new alias :command:`towncrier` (see :filename:`devel/activate-aliases.sh`).

devel/activate-aliases.sh

@@ -1,4 +1,5 @@
 #!/bin/bash
 
-alias upytest="uv run pytest"
-alias docbuild="uv run docbuild"
+alias upytest="uv run --frozen pytest"
+alias docbuild="uv run --frozen docbuild"
+alias towncrier="uv run --frozen towncrier"