feat: add api to concatenate audio files

[Traviskn]

Refs #1043

⚠️ Breaking changes ⚠️

• None

Introduced changes

• Add concatAudioFiles(inputPaths, outputPath): Promise<string> exported from the package root, joining a list of compatible local audio files into a single output file. Pairs naturally with the recorder's rotateIntervalBytes option to stitch rotated segments back into one file after recording.
• Implement the underlying engine in C++ (core/utils/AudioFileConcatenator) using the bundled FFmpeg, exposed to JS through a new AudioFileUtilsHostObject and wired up in AudioAPIModuleInstaller as the createAudioFileUtils JSI global.
• Add a web stub that rejects with a clear "not supported on web" error, plus mock + Jest coverage in tests/mock.test.ts, and a C++ unit test (common/cpp/test/src/utils/AudioFileConcatenatorTest.cpp).
• Add docs page packages/audiodocs/docs/utils/file-concatenation.mdx and cross-link it from the rotateIntervalBytes section of the audio recorder docs.
• Minor: exclude common/cpp/test/build from format:*:common and cpplint.sh so local C++ test builds don't trip linting/formatting.

Checklist

• Linked relevant issue (discussion Concatenate/Combine multiple audio files into 1 #1043)
• Updated relevant documentation
• Added/Conducted relevant tests
• Performed self-review of the code
• Updated Web Audio API coverage
• Added support for web (stub that rejects with a clear message)
• Updated old arch android spec file

[mdydek]

some changes needed before proper review, but at first glance it looks solid

[Traviskn]

Updated this PR with the recommended changes!

[mdydek]

impressive work, wonderful contribution! Only few nitpicks from the linter

[mdydek]

unfortunately, have to revert approve, code looks good, but it concats only m4a files (ffmpeg is not setup for wav and flac formats, miniaudio handles them and it fails because it meets unknown data), can you add also concatenating those formats, miniaudio operates on higher level than ffmpeg so it should be fairly simple. Also it would make us less dependent on ffmpeg, which is always better

[Traviskn]

Unfortunately miniaudio only supports WAV encoding (mentioned in the features list on their README and verified in code https://github.com/mackron/miniaudio), so while I was able to use it for WAV files I still needed to use ffmpeg for concatenating other file formats. I tested WAV and FLAC and both were working. I also ran into a consistent cocoa pods error when installing into a local test app and included a fix in the download-prebuilt-binaries.sh script

[Traviskn]

The latest push should address all the comments/requested changes. Let me know if any more changes are needed, happy to make any adjustments!