fix(player): prevent black screens during rapid playlist navigation

[kcng0]

Summary

• serialize built-in video controller initialization, promotion, preloading, and disposal
• reject stale async work and keep at most the current plus one preloaded controller alive
• expose initialization failures with a Retry action instead of an indefinite black/loading screen
• add ordered and shuffle regression coverage for repeated rapid Next actions
• prepare release version 1.0.22+27 and update the playback lifecycle invariant

Verification

• flutter analyze
• flutter test (261 tests passed)
• flutter build apk --release (68.8 MB APK)
• git diff --check

Release

After this PR is merged, tag v1.0.22 to trigger the GitHub release workflow.

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