Release 7.8 - Preview Trimming Controls

🎯 Improved Video Trimming Controls
Fine-tune your edits with new keyboard shortcuts in the preview window:
    •    Hold Shift + click skip → jump 1 second
    •    Hold Ctrl / Command + click skip → move frame-by-frame

Much easier to dial in exact IN/OUT points 👍

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🛠️ Small Improvements
    •    Loading state centered in preview
    •    Minor UI polish and fixes