ClearChat Home v1.5.1 RC2

Final Home release-candidate cleanup patch.

Changes:
- Functional sidebar theme buttons for Hybrid, Light, Dark, and System.
- Sidebar theme dropdown stays synchronized with quick buttons.
- Theme changes apply immediately and save automatically.
- Removed duplicate full theme selector from Settings; Settings now explains theme is controlled from the sidebar.
- Improved browser notification status wording for HTTPS, blocked, unsupported, and enabled states.
- Added Test Notification button alongside Enable Browser Notifications.
- Improved updater auto-refresh behavior after successful patch uploads.
- Version bumped to 1.5.1-rc2-home.

Apply through the ClearChat updater or manually extract into the ClearChat app root.
