v1.2.0 - Entry activity and editor polish

Every changelog entry now shows its life story, and the editor stops guessing about your intent.

Added

• Activity timeline on every changelog entry: who created it and how (GitHub webhook auto-draft, import, AI generation, or a person), plus every edit, publish and status change since - sourced from the audit log, so it cannot drift from reality

Changed

• The save button is dirty-aware: disabled until something actually changes, then comes alive; label reads "Save draft" only while the entry is a draft, "Save changes" once published
• Imported entries now carry their GitHub release provenance (release tag and repo) instead of looking hand-written

Fixed

• No-op saves no longer fire API calls or pollute the entry's activity with phantom "Edited" events
• Activity panel no longer refetches on every keystroke in the editor
• Save button no longer shifts layout when toggling between enabled and disabled

Docs: Changelog guide