[main] Upgrade important CI environment

[github-actions]

This PR upgrades important dependencies of the CI environment.

[Lee-W]

According to discussion in #contributors, we want to use uv==0.11.8

[potiuk]

Holding this PR until the global 4-day cooldown lifts for uv 0.11.8.

Background: #66042 bumped uv to 0.11.8 manually with a temporary uv = "12 hours" cooldown override under [tool.uv.exclude-newer-package] and [tool.uv.pip.exclude-newer-package] in pyproject.toml (flagged REMOVE BY 2026-05-01) so the freshly-published 0.11.8 could be adopted as the floor without waiting on the project-wide window. After rebasing this PR onto current main, the bot's pre-cooldown resolution still pins uv to 0.11.7, which would now be a downgrade.

Plan:

1. Wait until the 4-day cooldown has passed for uv 0.11.8 (≈ 2026-05-01).
2. Re-run the upgrade bot so the resolution picks 0.11.8 (or whatever is then latest outside cooldown) cleanly.
3. Remove the uv = "12 hours" overrides in [tool.uv.exclude-newer-package] and [tool.uv.pip.exclude-newer-package] — redundant once the global window covers 0.11.8.
4. Proceed with the normal review/merge.

Leaving as draft in the meantime.

---

Drafted-by: Claude Code (Opus 4.7); reviewed by @potiuk before posting