Major Updates:
- Extend year support to 2026 (2017-2026 range)
- Fix SIGKILL signal handler issue
- Add comprehensive local development guide

Features:
- 2026 holiday data support (120 holidays)
- Verified TaiwanCalendar CDN integration

Bug Fixes:
- Remove uncatchable SIGKILL handler
- Ensure GracefulShutdown stability

Documentation:
- Add 2026 support update report
- Add local development guide
- Update all technical documentation