Prepare 1.2.0 release

[nickotmazgin]

Summary

• bump metadata version to 1.2.0 and record changes in README/CHANGELOG
• update translation template header to new version

Testing

• ./build.sh

---

Note

Prepare 1.2.0 release: bump metadata version and update changelog/README and translation template headers.

• Release prep:
  • Bump extension version in metadata.json to 1.2.0 (version: 6, version-name: 1.2.0).
• Docs:
  • Update CHANGELOG.md with 1.2.0 entry (notes on HTML sanitization and repository security tooling).
  • Update README.md changelog section with 1.2.0 highlights.
• i18n:
  • Update translation template header locale/clipflow-pro.pot Project-Id-Version to 1.2.0.

^{Written by Cursor Bugbot for commit 68f38be. This will update automatically on new commits. Configure here.}