fix: announce ffmpeg loading state

[saurabhhhcodes]

Summary\n- announce ffmpeg loading state during export and preview flows\n- make the video editor feel less silent while work is running\n\n## Validation\n- reviewed the editor component diff\n- no unrelated app changes

[github-actions]

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[github-actions]

⚠️ PR Format Issues — @saurabhhhcodes

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