Install uv with astral-sh/setup-uv action in CI

[TheJulianJES]

Proposed changes

• This PR replaces the curl | sh to install uv with the astral-sh/setup-uv action, like we use for all zigpy repos.
• And for the pytest jobs, their separate install step is dropped, as they already get uv from the cached venv (due to being part of the dev extra).
• For testing, this PR should hopefully show that everything is working as expected. 😄
  • EDIT: See: https://github.com/puddly/serialx/actions/runs/38214726910/job/114696697358?pr=129

Detailed AI-generated PR description

A recent CI run on dev failed in prepare-base because the uv install script download hit a connection reset, which left uv missing for the rest of the job: https://github.com/puddly/serialx/actions/runs/37135339486/job/111238619586

This replaces curl -LsSf https://astral.sh/uv/install.sh | sh with astral-sh/setup-uv (already used by the docs workflow), which retries its version manifest fetch, downloads uv from the Astral mirror with a fallback to GitHub Releases, and verifies checksums:

• prepare-base and compile-esphome install uv with setup-uv, only on a cache miss like the step that uses it. Its own cache is disabled since the venv/binary is already cached.
• pytest and pytest-esphome drop their uv install step entirely. uv is part of the dev extra, so it's already in the cached venv, and every uv call in those jobs runs after the venv is activated (the curl-installed copy was shadowed by venv/bin/uv anyway).

The docs workflow is also bumped from setup-uv v8.1.0 to v10.2.0 to keep both on the same pin. It sets enable-cache: true explicitly, so the v9/v10 cache default changes don't affect it.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.33%. Comparing base (b853b11) to head (2a4e819).
⚠️ Report is 1 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #129      +/-   ##
==========================================
+ Coverage   94.32%   94.33%   +0.01%     
==========================================
  Files          25       25              
  Lines        4337     4345       +8     
==========================================
+ Hits         4091     4099       +8     
  Misses        246      246              

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[TheJulianJES]

For testing, this PR should hopefully show that everything is working as expected

The other PR already cached the venv. This run here shows that setup-uv is working as expected. The prek/ruff failure is unrelated and only happened because the newly generated venv happened to pick up a newer ruff version. This should be fixed separately. This PR would be ready.

For Prek/ruff fixes, see both:

• Run prek hook tools from the locked dev extra #130
• Bump ruff to 0.17.0 #131