This commit fixes a critical `ImportError` that prevented the bot from starting. The error was caused by the `agenda.py` module attempting to import calendar ID variables that were not being loaded into the application's configuration.
The fix involves:
- Updating `talia_bot/config.py` to correctly load the `WORK_GOOGLE_CALENDAR_ID` and `PERSONAL_GOOGLE_CALENDAR_ID` from the environment.
- Removing the obsolete `CALENDAR_ID` variable from the configuration.
- Updating `talia_bot/modules/calendar.py` to import and use the new, more specific `WORK_GOOGLE_CALENDAR_ID` as its default, ensuring consistency with the rest of the application.
