fix(app): preserve memidb event listeners

[OskarEichler]

What this fixes

Removing an IndexedDB fallback listener that was never registered no longer deletes the last real listener. The prior findIndex() result of -1 was passed directly to splice(-1, 1), silently suppressing a legitimate request or transaction callback.

Implementation

Only splice the listener array when a matching listener was found. Registered-listener removal behavior is unchanged.

Verification

The exact baseline regression registers two success listeners, removes an unrelated callback, and observes that the second real listener is never called. Both listeners run with this change. Complete repository gates pass:

• yarn lerna:prepare
• yarn tests:jest --runInBand — 104 suites, 1,480 tests, 31 snapshots
• yarn tsc:compile
• yarn tsc:compile:consumer
• yarn lint:deps
• yarn reference:api
• yarn compare:types
• focused ESLint
• git diff --check

Compatibility

No public API/type or breaking change. This aligns the fallback EventTarget with standard no-op removal semantics.

[mikehardy]

Hey @OskarEichler 👋

Thanks for the PR - this looks like a real problem to me. I ran local Jest/unit plus the android/ios/macos e2e suite against it here and it came out clean. Pending CI, then I'll merge.

Cheers

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.47%. Comparing base (81beeca) to head (cd1ef86).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #9270      +/-   ##
============================================
- Coverage     68.50%   68.47%   -0.03%     
  Complexity     1915     1915              
============================================
  Files           522      523       +1     
  Lines         38116    38136      +20     
  Branches       5189     5189              
============================================
+ Hits          26108    26110       +2     
- Misses        10222    10241      +19     
+ Partials       1786     1785       -1     

Flag	Coverage Δ
android-native	63.76% <ø> (ø)
e2e-ts-android	54.00% <ø> (ø)
e2e-ts-ios	53.50% <ø> (ø)
e2e-ts-macos	49.67% <100.00%> (-0.01%)	⬇️
ios-native	68.79% <ø> (+0.01%)	⬆️
ios-ruby	100.00% <ø> (ø)
jest	46.37% <50.00%> (+0.10%)	⬆️

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