[Feature]: Add an in-app release notes history

[spaansba]

Problem

Release notes are only visible while hovering an available nightly update. Once the app is up to date, there is no persistent in-app place to review current or previous releases.

Proposed experience

Add a full-screen What’s New view, reachable from Settings and from a View all release notes link in the update hover.

• Show previous releases newest-first
• Group entries into Features, Fixes, and Other
• Omit chore entries from the in-app view
• Keep changelog content and ordering identical across platforms
• Default to stable releases with an optional nightly filter
• Lazy-load or paginate older nightly releases
• Keep links to the corresponding GitHub release

The history should remain available when no update is pending.