Add SyncYomi integration with settings UI and automatic sync triggers

[dodmann]

Summary

• Add a dedicated SyncYomi settings section to the server settings page: enable/disable toggle, server address, API key, auto-sync interval, per-data-type sync toggles (manga, chapters, tracking, history, categories), and trigger configuration (chapter read, chapter open, client start, client resume)
• Add SyncTriggerHandler component mounted at the app root that fires sync automatically based on the configured triggers, reading current settings via the server settings subscription
• Show a persistent "Syncing library..." progress toast and a completion/error toast when the syncStatusChanged subscription reports a final state
• Add startSync GraphQL mutation and SyncStatusSubscription to RequestManager
• Extend the server settings GraphQL fragment with all SyncYomi fields

Test plan

• Navigate to Settings → Server and verify the SyncYomi section appears with all controls
• Set a valid SyncYomi server address and API key, save, and confirm the settings persist
• Enable "Trigger on client start" — reload the app and verify sync fires automatically
• Switch browser tabs away and back — verify "Trigger on client resume" fires sync
• Enable "Trigger on chapter read" — mark a chapter as read and verify sync is triggered
• Verify the progress toast shows during sync and is replaced by a success/error toast on completion