fix(client): add anti-echo guard for video syncing

[AbdulRashidReshamwala]

Added an anti-echo guard to prevent play/pause event spams.

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Note

Low Risk
Small, localized client-side state-sync change limited to play/pause handling; main risk is missing edge cases where the guard could mask legitimate state transitions.

Overview
Adds an anti-echo guard in video.vue to stop play/pause state from repeatedly re-triggering itself when the native <video> events and the @Watch('playing') watcher race.

This introduces an isVideoSyncing flag: native playing/pause listeners temporarily set the flag while they dispatch this.$accessor.video.play()/pause(), and the watcher now bails out when syncing to avoid event spam and state thrash (notably on Safari where video.paused can lag).

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