This commit resolves the TODO in the `checkTimetableChangesForUser` function in `Botrun/BotStart.go`.
The new implementation fetches the user's timetable by calling the `Untis.Auth` and `Untis.Timetable` functions. It then compares the new timetable with the previous one and sends a notification if there are any changes.
As part of this change, the `Bot` directory was renamed to `Untis` to follow Go conventions, and the import paths were updated in `Botrun/BotStart.go` and `main.go`. The `.gitignore` file was also updated to ignore the build artifact.
