chore(release): bump version to 1.2.0 and modernize mobile UI

[ankhang0704]

Summary

Release 1.2.0:

• Consolidated Pull/Push confirmation modals into SyncConfirmModal and result modals into SyncResultModal (~750 redundant lines deleted).
• Replaced all inline CSS styles with semantic Obsidian CSS classes and added mobile full-width responsive layouts with >=44px tap targets.
• Embedded expandable change inspection and category filtering directly in SyncDashboardModal, eliminating mobile modal stacking.
• Refactored SettingsTab into declarative definitions, cutting ~250 lines while preserving UI-TOKEN-002 compatibility.
• Quality gates: 44 test files, 482 passing tests, 0 lint warnings, clean build.
• All version files synchronized to 1.2.0.