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>

scripts/generate_ics.py

@@ -60,11 +60,16 @@ def _iter_date_ranges(days: Sequence[dict]) -> Iterator[Tuple[dict, dict]]:
     yield fr, to
 
 
-def generate_ics(days: Sequence[dict], filename: Text) -> None:
+def generate_ics(
+    days: Sequence[dict],
+    filename: Text,
+    cal_name: str = "中国法定节假日",
+    cal_desc: str = "中国法定节假日数据，自动每日抓取国务院公告。",
+) -> None:
     """Generate ics from days."""
     cal = Calendar()
-    cal.add("X-WR-CALNAME", "中国法定节假日")
-    cal.add("X-WR-CALDESC", "中国法定节假日数据，自动每日抓取国务院公告。")
+    cal.add("X-WR-CALNAME", cal_name)
+    cal.add("X-WR-CALDESC", cal_desc)
     cal.add("VERSION", "2.0")
     cal.add("METHOD", "PUBLISH")
     cal.add("CLASS", "PUBLIC")