Themes enhancement

![Screenshot_2025-08-17-20-04-34-437_net.waterfox.android.release-edit.jpg](https://github.com/user-attachments/assets/7a4659c7-a875-40ea-96a6-bffc3d9af6e6)

Dark/Light custom themes, Custom theme colors by users with hex color support.
I like the green themes, color suggestions of it:
- #00aa00
- #004000