chore: keep manual enhancement labels and accept two-digit versions in PR titles

[paulbalandan]

Description
This PR changes some config in carson.yml:

• auto-labeler: adds sync_exempt: [enhancement]. perf: PRs still get the label, and sync no longer removes an enhancement a maintainer added by hand.
• pr-title-linter: the pattern is now anchored as a whole and accepts multi-digit version parts. The accepted title types, scope characters, [x.y] prefix, and ! are unchanged.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value (without duplication)
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide