Fix: use correct API route for audio requests

[iprasannamb]

Summary

Problem

• Secure audio requests were sent to an incorrect endpoint (/audio/:filename instead of /api/audio/:filename)
• Admin audio download used a non-API route for audio files.
• On fetch failure, the component did not transition to an error UI.

Changes

• Updated protected audio fetch endpoint from /audio/:filename to /api/audio/:filename in ProtectedRoutes component.
• Added state reset before each fetch attempt to avoid stale UI.

Checklist:

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[gemini-code-assist]

Code Review

This pull request updates the audio fetching logic to use the /api/audio/ endpoint and introduces error handling and state management for the ProtectedAudio component. Feedback focuses on preventing memory leaks in useEffect by using a cancellation flag and ensuring that filenames are properly encoded when constructing API endpoints to handle special characters.

[iprasannamb]

@pradeeban , Could you please review this ?