FCE-2981: Mobile SDK improvements

[MiloszFilimowski]

Description

• ts-client: Add dedicated tsup.config.ts with a separate React Native bundle (index.react-native.mjs) that inlines all dependencies; add react-native and exports fields to package.json
• mobile-client: Bump @fishjam-cloud/react-native-webrtc 0.25.0 → 0.25.4, add react-native-url-polyfill and register it in the polyfill entrypoint, pin fast-text-encoding to exact version

Motivation and Context

The @bufbuild/protobuf/wire import was breaking under the React Native bundler because tsup didn't produce a self-contained RN build. A dedicated RN output with all deps inlined fixes the resolution issue. The URL polyfill and WebRTC bump address additional RN runtime compatibility gaps.

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-2981 Mobile SDK improvements

[Copilot]

Pull request overview

This PR improves React Native compatibility for the SDK by producing a dedicated self-contained React Native build of @fishjam-cloud/ts-client (to avoid Metro/deep-import resolution issues) and updating the mobile client’s runtime polyfills and WebRTC dependency versions.

Changes:

• Add packages/ts-client/tsup.config.ts to build both a standard ESM output and a dedicated React Native ESM bundle with dependencies inlined.
• Update @fishjam-cloud/ts-client package.json to expose a React Native entry via react-native + exports, and switch build to use the config file.
• Update mobile client deps: bump @fishjam-cloud/react-native-webrtc, add react-native-url-polyfill, and pin fast-text-encoding.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
yarn.lock	Reflects the mobile-client dependency updates (webrtc bump, URL polyfill addition, exact fast-text-encoding).
packages/ts-client/tsup.config.ts	Introduces a dual build, including a dedicated RN bundle with noExternal to inline deps.
packages/ts-client/package.json	Adds RN entry + exports, removes inline tsup config, and updates build script to run tsup via config.
packages/mobile-client/src/webrtc-polyfill.ts	Registers react-native-url-polyfill/auto in the polyfill entrypoint.
packages/mobile-client/package.json	Bumps @fishjam-cloud/react-native-webrtc, adds react-native-url-polyfill, and pins fast-text-encoding.

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