feat(whiteboard): two-finger scroll

[BrayanDSO]

Purpose / Description

Feature present in the old whiteboard that people missed

Approach

I didn't want to think too much, so I followed the approach used by the old whiteboard

Anki-Android/AnkiDroid/src/main/java/com/ichi2/anki/Whiteboard.kt

Line 324 in 2afb4ad

private fun reinitializeSecondFinger(event: MotionEvent) {

After that, I added support for interacting with the screen with just one finger if stylus mode is enabled

How Has This Been Tested?

Galaxy Tab S9, Android 16

Screen_Recording_20260130_152118_AnkiDroid.mp4

Checklist

Please, go through these checks before submitting the PR.

• You have a descriptive commit message with a short title (first line, max 50 chars).
• You have commented your code, particularly in hard-to-understand areas
• You have performed a self-review of your own code
• UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• UI Changes: You have tested your change using the Google Accessibility Scanner

[david-allison]

I'm happy, one borderline non-nit. Thanks!!

[david-allison]

One question, but still good to go

[criticalAY]

Thanks!