feat: add calendar sync triggers and visual type filtering

[h4yfans]

What

Add Google Calendar auto-sync on focus, resume, and manual refresh; add visual type filtering to calendar views; implement event deletion.

Why

Calendar sync was only triggered by periodic intervals (every 5 minutes). Users expect real-time updates when the app regains focus or comes back from background. Added ability to filter calendar items by type (events, tasks, reminders, snoozed items) and delete calendar events.

How

• New sync triggers: window focus, app resume, manual refresh button
• Visual type metadata and filtering in calendar views
• Delete event dialog with confirmation
• New mutation hook for delete operations
• Updated tests and IPC contracts

Type

• feat

Test plan

• Calendar syncs when app window regains focus
• Calendar syncs when app resumes from background
• Manual refresh button triggers sync
• Visual type filters work correctly in all calendar views
• Event deletion dialog appears and works
• Tests pass: pnpm test (7135 tests)
• Type checking passes: pnpm typecheck
• IPC contracts validated: pnpm ipc:check

Checklist

• Self-reviewed code
• No hardcoded secrets or credentials
• Files follow 500 LOC guideline
• Immutable patterns used throughout