Bug: Alarm does not ring automatically at scheduled time (Preview works)

### Description

While working on the fix for alarm saving in #896, I noticed that alarms still do not ring automatically when their scheduled time arrives.

The alarm is now correctly saved to the ISAR database and appears in the alarm list, but the ringtone is never triggered automatically.

The ringtone only plays when using the **Preview Alarm** feature.

This suggests the issue may be related to alarm scheduling or the native alarm trigger mechanism rather than the database or UI.

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### Steps to Reproduce

1. Run the application on a physical Android device
2. Create a new alarm for 1–2 minutes in the future
3. Save the alarm
4. Wait until the scheduled time

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### Expected Behavior

The alarm should automatically trigger and play the ringtone at the scheduled time.

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### Actual Behavior

The alarm does not ring automatically.

The ringtone only plays when the **Preview Alarm** button is used.

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### Notes

- The alarm is correctly stored in the **ISAR database**
- The alarm appears correctly in the **alarm list UI**
- The alarm persists after restarting the app

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### Logs

During debugging the following logs appear:

STOPPED IF CONDITION with latest = TimeOfDay(...)
FLUTTER CALLED CANCEL ALARMS

### Environment

Flutter version: 3.22.2 (via FVM)
Platform: Android
Device: Physical Android device
Android SDK: 34+

I would be happy to investigate and work on fixing this issue.

### Screenshots

_No response_