feat(CI): 👷 Create a reusable workflow for UV and make UV lockfile frozen

[Paillat-dev]

Summary

Use frozen lockfile to reduce risk of supply chain attacks

Information

• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed).
• This PR is not a code change (e.g. documentation, README, typehinting,
  examples, ...).

Checklist

• I have searched the open pull requests for duplicates.
• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• If type: ignore comments were used, a comment is also left explaining why.
• I have updated the changelog to include these changes.

[Paillat-dev]

[Copilot]

Pull Request Overview

This PR creates a reusable GitHub Actions workflow for UV dependency management and enables frozen lockfile mode to enhance supply chain security. The changes consolidate UV setup and sync operations across multiple workflow files.

Key Changes:

• Created a new reusable action (.github/actions/sync-uv/action.yml) that handles UV installation and dependency synchronization with configurable groups and extras
• Updated all workflow files to use the new reusable action and downgraded Python version from 3.14 to 3.13
• Enabled frozen lockfile mode by default to prevent unexpected dependency updates

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
.github/actions/sync-uv/action.yml	New reusable action that installs UV and syncs dependencies with frozen lockfile enabled by default
.github/workflows/sync-guild-features.yml	Refactored to use new UV action with dev and ci groups
.github/workflows/lib-checks.yml	Updated all jobs to use new UV action with dev group
.github/workflows/docs-localization-upload.yml	Migrated to new UV action with docs groups and speed/voice extras
.github/workflows/docs-localization-download.yml	Migrated to new UV action with docs groups and speed/voice extras
.github/workflows/docs-checks.yml	Updated to use new UV action with dev and docs groups

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