[CI] Stop tracking root uv lockfile

[jiayuasu]

Did you read the Contributor Guide?

• Yes, I have read the Contributor Rules and Contributor Development Guide

Is this PR related to a ticket?

• No:
  • this is a CI update. The PR name follows the format [CI] my subject

What changes were proposed in this PR?

• Stop tracking the root uv.lock, which is used only for documentation and development tooling.
• Ignore locally generated root lockfiles and remove the root uv Dependabot configuration.
• Keep make update-deps able to refresh local dependencies through uv sync --upgrade.
• Update the developer guide to describe locally resolved dependency versions.

This avoids recurring Dependabot alerts and update churn for transitive documentation dependencies. Documentation and development environments will resolve the latest compatible versions when refreshed.

How was this patch tested?

• prek run --files .gitignore .github/dependabot.yml Makefile docs/setup/compile.md
• git diff --check

Did this PR include necessary documentation updates?

• Yes, the developer guide now reflects that dependency versions are resolved locally rather than committed in a root lockfile.