- Refactor `main.sh` to support `reminders` and `calendar` commands,
displaying tmux popups with localized titles and current date/time.
- Add `show_reminders.sh` and `show_calendar.sh` scripts to render
reminders and 2-week calendar views using `rem`.
- Update `tmux-remind.tmux` to bind `prefix + r` for reminders and
`prefix + c` for calendar popups.
- Improve script robustness with `set -euo pipefail` and dynamic script
directory resolution.
