Fix controls: prevent duplicate bindings

[manocormen]

Purpose / Description

This PR fixes the following bug: In Controls, it is currently possible to end up with conflicting bindings.

For instance, if you

1. assign "swipe down" to both "Toggle red -> Q" and "Toggle orange -> A"
2. assign "swipe down" to "Toggle green -> BOTH"

you end up with "swipe down" assigned to both "Toggle orange -> A" and "Toggle green -> BOTH", i.e. duplicate bindings. This happens because we're only removing a single conflicting binding.

Fixes

• Third bug in Improve the dialogs in the Controls screen #20504

Approach

When we add a new binding, instead of removing a single conflicting binding, we now retrieve for and remove all conflicting bindings. I did this by introducing a couple of helpers: getPreferencesAssignedTo() and removeDuplicateBindings().

After the fix, the steps above don't produce duplicates anymore:

Screen_recording_20260415_143803.mp4

How Has This Been Tested?

I manually tried various combinations of gesture/key assignments on my physical device.

I ran:

./gradlew jacocoUnitTestReport                      
./gradlew lintRelease ktlintCheck

Checklist

• 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 NA

[david-allison]

Really solid, thank you!!

[mikehardy]

LGTM - thank you!