With tz: Use the specified timezone (e.g., "Asia/Shanghai").
Without tz: Use the local timezone (datetime.now().astimezone().tzinfo) instead of defaulting to UTC
When schedule.tz is present, use the specified timezone to calculate the next execution time, ensuring scheduled tasks trigger correctly across different timezones.
Markdown heading syntax (#) is not properly rendered in Feishu interactive
cards. Convert headings to div elements with lark_md format (bold text) for
proper display.
- Add _HEADING_RE regex to match markdown headings (h1-h6)
- Add _split_headings() method to parse and convert headings to div elements
- Update _build_card_elements() to process headings before markdown content
Ahwei