Feature: add GET /database/timetable/timetables endpoint for TimetableListPage.

- Added router file: routers/database/timetable/timetables.py
- Wired new timetable router from run/routers.py
- Provided pragmatic /database/timetables/timetables GET and GET/{id} shapes that return Timetable lists

Note: TimetableListPage uses /database/timetable/timetables (singular timetable segment) even though the underlying router is now under /database/timetables. Curl checks below use that path.