Fix moved recurring Google Calendar occurrences

[martin-forge]

Summary

Fixes #1696.

• Keeps the Google Calendar recurring master event on its original DTSTART/RRULE when one scheduled occurrence is moved.
• Adds EXDATE entries for original occurrence dates that should no longer render on the master series.
• Creates or updates a detached one-off Google Calendar event for the currently moved occurrence.
• Cleans detached exception metadata during completion, skip, delete, archive, and unlink flows.

Related to #1509, #1921, and #1925. This PR is intentionally scoped to recurring Google Calendar exceptions only; the direct frontmatter reconciliation fix is separate.

Tests

• npm test -- --runInBand tests/services/TaskCalendarSyncService.test.ts tests/unit/services/taskUpdatePlanning.test.ts tests/unit/issues/issue-google-calendar-archive-reliability.test.ts tests/unit/issues/issue-google-calendar-duplicate-sync.test.ts tests/unit/issues/issue-1696-gcal-recurring-reschedule.test.ts
• npm run typecheck
• npm run lint
• npm run build:test
• vault-python 7 System/Scripts/vault/scan_public_pr.py --repo /Users/martin/Developer/tasknotes-main --base origin/main --head martin-forge/issue-1696-recurring-calendar-exceptions-v2