Improve the "Learn ahead limit" and "Timebox time limit" dialogs

The "Learn ahead limit" and "Timebox time limit" dialogs

• Change them to input steppers (like in https://github.com/ankidroid/Anki-Android/issues/20477).
• Prevent the user from typing more than 3 digits.
• Replace "OK with "Save".
• Add a toggle to disable the limits like the screenshot bellow.
• Look into the leading zero issues discussed in https://github.com/ankidroid/Anki-Android/pull/20520#issuecomment-4095597664. I don't know if the fix there somehow fixes these dialogs too, but if it doesn't consider adding it to these.