fix(macOS): allow .m4a mic/system audio sidecars through the media allowlist

[Priyangshu-7]

Description

Add .m4a support to Recordly's local media content-type allowlist so macOS microphone/system-audio sidecar files can be recognized as audio media.

Motivation

On macOS, audio captured alongside a recording can be stored as .m4a files. The existing media allowlist did not include the .m4a extension, causing these files to be treated as unsupported local media.

This change maps .m4a to the audio/mp4 MIME type and adds regression tests for the media type detection and local media path validation.

Type of Change

• New Feature
• Bug Fix
• Refactor / Code Cleanup
• Documentation Update
• Other (please specify)

Related Issue(s)

Not linked to an issue.

Screenshots / Video

Not applicable. This is a backend/media-type handling change with no UI changes.

Testing Guide

Run the Electron test suite:

npx vitest --run electron/

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->

## Summary by CodeRabbit

* **Bug Fixes**
  * Added support for `.m4a` audio files, including recognizing them as `audio/mp4` and accepting them as local media paths.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository: webadderallorg/Recordly/.coderabbit.yaml

Review profile: ASSERTIVE

Plan: Advanced

Run ID: 6b5f3930-3737-4d48-8a34-a08e6fc99996

📥 Commits

Reviewing files that changed from the base of the PR and between 1888428 and 955ae13.

📒 Files selected for processing (2)

• electron/mediaTypes.test.ts
• electron/mediaTypes.ts

Included review availability: Your plan provides up to 10 included reviews per hour; 9 remain after this review.

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📝 Walkthrough

Walkthrough

The media type map now associates .m4a files with audio/mp4. Tests check the mapping and local media path handling.

Changes

M4A media support

Layer / File(s)	Summary
M4A content type mapping and tests electron/mediaTypes.ts, electron/mediaTypes.test.ts	The media type map adds .m4a with the audio/mp4 content type. Tests check this mapping and local media path handling.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~5 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to 955ae

The .m4a content type matches the media-serving and local-path behavior, which retains its existing file and permission checks. No actionable merge risk is evident.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the macOS-specific fix and the addition of .m4a support to the media allowlist.
Description check	✅ Passed	The description explains the change, motivation, type, testing approach, and why screenshots are not applicable. The checklist section is missing, but the description is otherwise complete.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create a new PR

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