Move all display/UX settings from browser localStorage to server-side
settings.json. Flat keys approach (Approach A) - adds 10 new keys to
DEFAULT_SETTINGS, requiring zero changes to existing load/save/patch
functions or API endpoints.
Key decisions:
- No federation settings sync (each server owns its own settings)
- Drop notificationPermission (browser API is source of truth)
- sidebarOpen defaults to None for auto-detect on first load
- No migration needed - users reset preferences
- Fix auto_open vs auto_open_created naming alignment
Verified compatible with muxplex v0.2.0 (1b5207b).
Brian Krabach