Added operators

Add operators for making it a scientific calculator. The calculator transforms into a scientific one when rotated.

The calculator uses Kivy for the UI and likely has orientation detection. Look for the main Kivy app file (maybe main.py) and the layout definitions. Check how the current calculator UI is built and where rotation events are handled. Adding scientific operators means extending the button grid and updating the expression parser to handle functions like sin, cos, log, etc. Test by rotating the app in an emulator or on a device.

索引モデルが issue の本文から書いたものです。