chore: finalize CHANGELOG.md for v1.0.0

[kirich1409]

Context

All changes accumulated since the beginning of the project sit under [Unreleased] in CHANGELOG.md. Before tagging v1.0.0 the changelog must be converted into a proper versioned section.

Acceptance criteria

• Rename [Unreleased] → [1.0.0] - <release date>
• Add a new empty [Unreleased] section at the top
• Verify every item in the existing list is still accurate (nothing removed, nothing missing)
• Add a comparison link at the bottom: [1.0.0]: https://github.com/AndroidBroadcast/Featured/releases/tag/v1.0.0
• Format follows Keep a Changelog 1.1.0

Notes

• Do this as the final step before bumping VERSION_NAME and pushing the tag
• The CHANGELOG content should match the GitHub Release body generated by the publish workflow