let users click on the timetable to select slots

**Is your feature request related to a problem? Please describe.**
When selecting of slots can be done just by clicking on slots on the time table, why give out buttons? I get its asthetically pleasing, but we can either:
1. let that go
2. Allow users to select and deselect slots both ways

**Describe the solution you'd like**
Why not just allow user to click on the time table to select labs, theory slots, and grey out slots there only

**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features you've considered.

**Additional context**

Start by running the application and locating the timetable UI and existing slot-selection behavior. Check how lab and theory slots are selected, deselected, and greyed out; done means users can perform those actions directly on timetable slots as well as through the existing controls, without breaking clash handling.

索引モデルが issue の本文から書いたものです。