feat(ios): add native PiP and Now Playing integration

[WhiteGiso]

Summary

Adds native iOS Picture in Picture support for the existing MPV-based player bridge and integrates system Now Playing / remote playback controls so playback state is reflected correctly in Control Center and lock screen.

PR type

• Reproducible bug fix
• UI glitch/bug fix
• Behavior bug/regression fix
• Small maintenance only, with no UI or behavior change
• Docs accuracy fix
• Translation/localization only
• Approved larger or directional change

Why

This change brings the iOS player closer to the expected native media experience:

• Picture in Picture works for supported playback on iPhone/iPad
• playback state is exposed to the system via Now Playing
• Control Center / lock screen controls stay in sync with actual playback
• playback transitions between inline player, PiP, and return to the app are handled natively on iOS

Issue or approval

Approved in #1268.

UI / behavior impact

• No UI change
• No behavior change
• UI changed only to fix a documented glitch/bug
• Behavior changed only to fix a documented bug/regression
• UI change has explicit maintainer approval
• Behavior change has explicit maintainer approval

Policy check

• I have read and understood CONTRIBUTING.md.
• This PR is small, focused, and limited to one problem.
• This PR is not cosmetic-only.
• Any UI change fixes a linked glitch/bug and includes visual proof, or this PR has no UI change.
• Any behavior change fixes a linked bug/regression or has explicit approval, or this PR has no behavior change.
• This PR does not bundle unrelated refactors, cleanups, formatting, or drive-by changes.
• This PR does not add dependencies, architecture changes, migrations, or product-direction changes without explicit approval.
• I listed the testing performed below.

Scope boundaries

Not changed in this PR:

• Android playback behavior
• liquid glass / profile switching
• unrelated player UI polish
• unrelated dependency or project setup changes
• MPVKit/ local/untracked files
• project.pbxproj local environment changes

Testing

Manual testing on iOS device:

• inline playback starts correctly
• Now Playing appears in Control Center / lock screen
• Picture in Picture starts from the iOS player flow
• returning from PiP restores the inline player
• seek controls in PiP and system controls work during playback
• playback state remains in sync with the system media UI

Screenshots / Video

Not a UI change.

Breaking changes

None.

Linked issues

Fixes #1268