Use uv image with Python 3.13 as base

ghcr.io/astral-sh/uv:0.10.4-python3.13-trixie-slim includes both uv and
Python 3.13, avoiding the need to download a managed Python at build time
which caused Docker builds in tests to be 3-4x slower.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

Author: adamtheturtle

src/mock_vws/_flask_server/Dockerfile

@@ -1,5 +1,4 @@
-FROM debian:bookworm-slim AS base
-COPY --from=ghcr.io/astral-sh/uv:0.10.4 /uv /uvx /bin/
+FROM ghcr.io/astral-sh/uv:0.10.4-python3.13-trixie-slim AS base
 # We set this pretend version as we do not have Git in our path, and we do
 # not care enough about having the version correct inside the Docker container
 # to install it.