refactor(audio_processing): replace pipe with temp files for FFmpeg p…

[joeyhacker]

…rocessing

This change replaces the previous pipe-based FFmpeg audio decoding approach
with temporary file operations to improve reliability, especially for
container formats like MP4/m4a.

Key reasons for this change:
1. MP4 container format requires random access to metadata (moov atoms) which is often located at the end of the file. Pipe streaming makes this access pattern impossible.
2. FFmpeg's format detection works more reliably with physical files compared to streamed input via pipes.
3. Temporary files provide better error diagnostics since the input can be preserved for debugging when failures occur.
4. Some FFmpeg codecs and filters behave differently with pipe input versus file input due to buffering differences.

The new implementation:
- Creates properly named temporary files with correct extensions
- Uses atomic write operations with flush()
- Implements comprehensive cleanup in finally blocks
- Provides better error messages when failures occur

This fixes issues with partial file errors ("offset 0x3f9: partial file")
that occurred during demuxing of m4a files in the pipe-based approach

What does this PR do?

Fixes # (issue)

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[Rocketknight1]

I think this makes sense for pipelines and I agree that media files often require seeking that is incompatible with piping/streaming. cc @eustlb for audio, WDYT?