FCE-2848; FCE-2849: Fix missing yarn build step in examples

[MiloszFilimowski]

Description

• Updated the examples README to be up to date.

Motivation and Context

Mobile client example READMEs had inconsistent and incomplete setup instructions — most notably minimal-react-native was missing the required yarn build and npx expo prebuild steps, which would cause the example to fail for new users.

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-2848 Fix missing yarn build step in examples

FCE-2849 Remove teamId from app.json in mobile examples

[Copilot]

Pull request overview

This PR updates mobile client example READMEs to ensure consistent and complete setup instructions. The primary issue addressed is that the minimal-react-native example was missing critical yarn build and npx expo prebuild steps that would cause setup failures for new users. Additionally, the PR standardizes formatting, corrects license references, and improves consistency across all mobile client examples.

Changes:

• Added missing yarn build and npx expo prebuild --clean steps to minimal-react-native example
• Consolidated installation steps and added yarn build to text-chat example
• Corrected license references from MIT to Apache License 2.0 and fixed LICENSE file paths from ../../LICENSE to ../../../LICENSE
• Standardized code block language from cmd to sh in fishjam-chat for consistency
• Updated .env.example formatting to remove placeholder values

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
examples/mobile-client/video-player/README.md	Added --clean flag to npx expo prebuild command for consistency
examples/mobile-client/video-player/.env.example	Removed placeholder value to match format of other examples
examples/mobile-client/text-chat/README.md	Consolidated installation steps, added yarn build step, corrected license reference and path, removed redundant "yarn start" section
examples/mobile-client/minimal-react-native/README.md	Added critical missing yarn build and npx expo prebuild --clean steps, corrected license reference and path, improved environment setup instructions
examples/mobile-client/fishjam-chat/README.md	Changed code block language from cmd to sh for consistency with other examples

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