Add native LiveKit calls on iOS and Android

[eleboucher]

• chore(call): vendor the native call plugin and its iOS frameworks
• feat(call): discover LiveKit transports and subscribe the call room
• feat(call): join MatrixRTC and distribute media keys
• feat(call): put both call engines behind one transport seam
• feat(call): add the call UI, controls and settings gate

Description

Fixes #

Type of change

• 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)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

AI disclosure:

• Partially AI assisted (clarify which code was AI assisted and briefly explain what it does).
• Fully AI generated (explain what all the generated code does in moderate detail).

[github-actions]

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