- Updated the scheduled message format in `config.ini.example` to support 5-field cron expressions and preset aliases, replacing the deprecated HHMM format.
- Improved the `MessageScheduler` class to parse and validate new schedule formats, logging warnings for deprecated usage.
- Adjusted the `ScheduleCommand` to display scheduled messages with their respective cron or preset labels.
- Added unit tests to ensure correct parsing and handling of various schedule formats, including legacy HHMM and cron expressions.
Add ScheduleCommand (DM-only by default). Displays configured scheduled
message times, target channels, message previews, and the current
advertisement interval. Read-only; does not modify schedule state.