fix: Sync no longer on leave study/background

[Giyutomioka-SS]

Purpose / Description

After returning from the study screen, onStartupResponse() was re-firing on every resume and triggering an unexpected sync. This fix prevents that by consuming the startup response after it's handled.

Fixes

• Fixes Sync is triggered when leaving the study screen #19854

Approach

When DeckPicker comes back to the foreground (e.g. after studying), the startup response flow re-emits and runs the startup code again, including auto-sync. The permissions branch already prevented this by clearing the response after use, but the success branch didn't. So after a long study session, coming back would trigger a sync again. Added the same "clear after use" line to the success branch so startup only runs once.

How Has This Been Tested?

Manually confirmed returning to deck list after study no longer triggers an unexpected sync.

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]

Great diagnostics!!

Is it feasible to handle this inside the ViewModel?

Could you also add a test, or a @NeedsTest