FCE-3322: Fix react native MediaStreamTrack

[MiloszFilimowski]

Description

• Re-export MediaStreamTrack from @fishjam-cloud/react-native-webrtc so mobile consumers get the RN-native track type.
• Override Track and RemoteTrack so their track field is typed as RNMediaStreamTrack instead of the web type.
• Override useCamera, useMicrophone, useScreenShare results (and middleware types) to use RN media types for startCamera/startMicrophone returns, videoTrack/audioTrack, and
  *Middleware setters.
• Move MiddlewareResult, TrackMiddleware, TracksMiddleware, TracksMiddlewareResult exports to the mobile overrides.

Motivation and Context

The mobile client was leaking the web MediaStreamTrack type through hooks and track objects, causing type mismatches for RN consumers. This aligns all media track types with
react-native-webrtc.

Documentation impact

• Documentation update required
• Documentation updated in another PR
• No documentation update required

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to
  not work as expected)

[linear]

FCE-3322

[Copilot]

Pull request overview

This PR fixes React Native type leakage by ensuring the mobile client surfaces React Native WebRTC media types (not DOM/web types) through its public hook results and track objects.

Changes:

• Re-export MediaStreamTrack from @fishjam-cloud/react-native-webrtc via the mobile client entrypoint.
• Update mobile override types (Track, RemoteTrack, and device hook results) so track, videoTrack, audioTrack, and startCamera/startMicrophone returns are typed as RNMediaStreamTrack.
• Move MiddlewareResult/TrackMiddleware/TracksMiddleware/TracksMiddlewareResult exports to the mobile override types and adapt hook wrappers to accept RN-typed middleware.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
packages/mobile-client/src/overrides/types.ts	Switches public mobile override types from web MediaStreamTrack to RN MediaStreamTrack, and defines RN-typed middleware/result types.
packages/mobile-client/src/overrides/hooks.ts	Wraps middleware setters and casts hook results so consumers see RN media types for tracks and middleware.
packages/mobile-client/src/index.ts	Re-exports MediaStreamTrack from RN WebRTC and re-exports middleware types from the mobile overrides instead of the web client.

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