Fix personal video call preview and layout

[AbdulKus]

What changed

• share one EGL context between camera capture and call renderers to fix the black local preview
• delay direct-video camera start until the tgcalls media graph is ready
• cache video sinks and detach the local sink in picture-in-picture mode
• align encryption emoji with the call branding row
• account for the navigation inset in the bottom controls so active circles are not clipped
• add subtle camera enable and switch animations

Validation

• git diff --check
• full ARM64 release build runs in GitHub Actions

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Preserve preview alpha when switching cameras

If the user taps the switch-camera button during the 220 ms preview appearance animation, this cancellation freezes localVideoWrap at its current alpha, while the replacement animation changes only its scale. Because localPreviewVisible is already true, subsequent state updates return without restoring the alpha, leaving the local preview partially or almost fully transparent until it is hidden and shown again.

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