fix: handle adhan audio cutting off for Fajr prayer

📝 Summary

Handles the issue of adhan audio cutting off in the middle for Fajr prayer

This solve issue: #1100

This PR addresses the issue where the adhan audio was cutting off in the middle during the Fajr prayer. It introduces the following changes:

In AdhanSubScreen.dart, a flag isFajrPray is added to check if the current salah index is 0 (Fajr prayer). The getAdhanDuration function is called with this flag to determine the appropriate duration.
In salah_workflow.dart, the isFajrPray flag is also used when calling getAdhanDuration to calculate the adhanEndTime.
In audio_mixin.dart, the getAdhanDuration function is modified to handle the Fajr prayer case. If the isFajrPray flag is true and the adhanName is not null, the '-fajr' suffix is appended to the adhanName.

💬 Description: Test the Fajr prayer adhan playback to ensure the audio does not cut off in the middle.

📷 Screenshots or GIFs (if applicable): [Provide any relevant screenshots or GIFs demonstrating the successful test case]

[x] Coding Standards: I have reviewed my code to ensure it follows the project's coding standards.
[x] Testing: I have tested the changes and they work as expected.
[x] Merge Conflicts: I have resolved any merge conflicts with the latest main/development branch.
[x] Branch Status: The branch is up-to-date with the target branch (main/development).