refactor(electron): use mp4 container instead of webm for encoded audio (#12247)

fix AF-2609
webm container with opus has limited support on Safari. Change to mp4 instead.

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

## Summary by CodeRabbit

- **New Features**
  - Audio recordings are now saved in MP4 format instead of WebM, improving compatibility with a wider range of devices and applications.

- **Chores**
  - Updated dependencies to use MP4 muxing tools in place of WebM.
  - Internal audio encoding utilities and references updated to support MP4 container format.

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

packages/frontend/core/package.json

@@ -66,6 +66,7 @@
     "lit": "^3.2.1",
     "lodash-es": "^4.17.21",
     "lottie-react": "^2.4.0",
+    "mp4-muxer": "^5.2.1",
     "nanoid": "^5.0.9",
     "next-themes": "^0.4.4",
     "query-string": "^9.1.1",
@@ -80,7 +81,6 @@
     "socket.io-client": "^4.8.1",
     "swr": "2.3.3",
     "tinykeys": "patch:tinykeys@npm%3A2.1.0#~/.yarn/patches/tinykeys-npm-2.1.0-819feeaed0.patch",
-    "webm-muxer": "^5.1.0",
     "y-protocols": "^1.0.6",
     "yjs": "^13.6.21",
     "zod": "^3.24.1"