Implements server-side database caching with 5-minute refresh intervals to
dramatically improve external calendar performance while keeping data fresh.
Backend changes:
- New external_calendar_cache table with ICS data storage
- Smart cache logic: serves from cache if < 5min old, fetches fresh otherwise
- Cache repository methods for get/update/clear operations
- Migration script for cache table creation
Frontend changes:
- 5-minute auto-refresh interval for background updates
- Manual refresh button (🔄) for each external calendar
- Last updated timestamps showing when each calendar was refreshed
- Centralized refresh function with proper cleanup on logout
Performance improvements:
- Initial load: instant from cache vs slow external HTTP requests
- Background updates: fresh data without user waiting
- Reduced external API calls: only when cache is stale
- Scalable: handles multiple external calendars efficiently
🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>
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