feat: Implement upcoming appointments feature for users

- Added `remove_done` function to clean up finished appointments in the database.
- Introduced `get_upcoming_for_user` function to retrieve upcoming appointments for a specific user.
- Updated `backend_server.py` to include a new endpoint for fetching user-specific upcoming events.
- Modified `blueprint.py` to render upcoming events in the user interface.
- Enhanced `terminplan.html` to display a list of upcoming appointments with relevant details and action links.
- Updated configuration to enable the new appointment planning feature.

Web/modules/terminplaner/blueprint.py

@@ -132,8 +132,12 @@ def main():
     if guard:
         return guard
 
+    current_user = session.get('username', '')
+    upcoming_events = appointment_service.get_user_upcoming_events(current_user) if current_user else []
+
     return render_template(
         'terminplaner.html',
         school_periods=cfg.SCHOOL_PERIODS,
-        current_user=session.get('username', ''),
+        current_user=current_user,
+        upcoming_events=upcoming_events,
     )