feat: add Hong Kong public holiday support

- Add scripts/fetch_hk.py to fetch HK holidays from 1823.gov.hk
- Make generate_ics() cal_name/cal_desc configurable
- Refactor update.py with REGIONS config; support --region cn|hk flag
- Generate hk/{year}.json and hk/{year}.ics under hk/ subdirectory

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

hk/2026.ics

@@ -0,0 +1,100 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+METHOD:PUBLISH
+CLASS:PUBLIC
+X-WR-CALDESC:香港公众假期数据，来源：香港特别行政区政
+ 府 1823.gov.hk。
+X-WR-CALNAME:香港公众假期
+BEGIN:VTIMEZONE
+TZID:Asia/Shanghai
+BEGIN:STANDARD
+DTSTART:19700101T000000
+TZOFFSETFROM:+0800
+TZOFFSETTO:+0800
+END:STANDARD
+END:VTIMEZONE
+BEGIN:VEVENT
+SUMMARY:一月一日假期
+DTSTART;VALUE=DATE:20260101
+DTEND;VALUE=DATE:20260102
+DTSTAMP;VALUE=DATE:20260101
+UID:2026-01-01/2026-01-02/NateScarlet/holiday-cn
+END:VEVENT
+BEGIN:VEVENT
+SUMMARY:農曆年初一假期
+DTSTART;VALUE=DATE:20260217
+DTEND;VALUE=DATE:20260220
+DTSTAMP;VALUE=DATE:20260217
+UID:2026-02-17/2026-02-20/NateScarlet/holiday-cn
+END:VEVENT
+BEGIN:VEVENT
+SUMMARY:耶穌受難節假期
+DTSTART;VALUE=DATE:20260403
+DTEND;VALUE=DATE:20260405
+DTSTAMP;VALUE=DATE:20260403
+UID:2026-04-03/2026-04-05/NateScarlet/holiday-cn
+END:VEVENT
+BEGIN:VEVENT
+SUMMARY:清明節翌日假期
+DTSTART;VALUE=DATE:20260406
+DTEND;VALUE=DATE:20260408
+DTSTAMP;VALUE=DATE:20260406
+UID:2026-04-06/2026-04-08/NateScarlet/holiday-cn
+END:VEVENT
+BEGIN:VEVENT
+SUMMARY:勞動節假期
+DTSTART;VALUE=DATE:20260501
+DTEND;VALUE=DATE:20260502
+DTSTAMP;VALUE=DATE:20260501
+UID:2026-05-01/2026-05-02/NateScarlet/holiday-cn
+END:VEVENT
+BEGIN:VEVENT
+SUMMARY:佛誕翌日假期
+DTSTART;VALUE=DATE:20260525
+DTEND;VALUE=DATE:20260526
+DTSTAMP;VALUE=DATE:20260525
+UID:2026-05-25/2026-05-26/NateScarlet/holiday-cn
+END:VEVENT
+BEGIN:VEVENT
+SUMMARY:端午節假期
+DTSTART;VALUE=DATE:20260619
+DTEND;VALUE=DATE:20260620
+DTSTAMP;VALUE=DATE:20260619
+UID:2026-06-19/2026-06-20/NateScarlet/holiday-cn
+END:VEVENT
+BEGIN:VEVENT
+SUMMARY:香港特別行政區成立紀念日假期
+DTSTART;VALUE=DATE:20260701
+DTEND;VALUE=DATE:20260702
+DTSTAMP;VALUE=DATE:20260701
+UID:2026-07-01/2026-07-02/NateScarlet/holiday-cn
+END:VEVENT
+BEGIN:VEVENT
+SUMMARY:中秋節翌日假期
+DTSTART;VALUE=DATE:20260926
+DTEND;VALUE=DATE:20260927
+DTSTAMP;VALUE=DATE:20260926
+UID:2026-09-26/2026-09-27/NateScarlet/holiday-cn
+END:VEVENT
+BEGIN:VEVENT
+SUMMARY:國慶日假期
+DTSTART;VALUE=DATE:20261001
+DTEND;VALUE=DATE:20261002
+DTSTAMP;VALUE=DATE:20261001
+UID:2026-10-01/2026-10-02/NateScarlet/holiday-cn
+END:VEVENT
+BEGIN:VEVENT
+SUMMARY:重陽節翌日假期
+DTSTART;VALUE=DATE:20261019
+DTEND;VALUE=DATE:20261020
+DTSTAMP;VALUE=DATE:20261019
+UID:2026-10-19/2026-10-20/NateScarlet/holiday-cn
+END:VEVENT
+BEGIN:VEVENT
+SUMMARY:聖誕節假期
+DTSTART;VALUE=DATE:20261225
+DTEND;VALUE=DATE:20261227
+DTSTAMP;VALUE=DATE:20261225
+UID:2026-12-25/2026-12-27/NateScarlet/holiday-cn
+END:VEVENT
+END:VCALENDAR