### What
- Drag files onto the promptbox on the Image, Video, and Audio create
pages to add them as references - same look and behavior as the webapp
- On those pages the promptbox is now the only drop target; dropping
elsewhere does nothing
- Every other page keeps the existing upload-modal behavior
### Notes
- The webapp's drop code doesn't work as-is on desktop - Tauri
intercepts file drags before the page sees them, so desktop needed its
own path
- Both now share one component, so the two apps stay in sync going
forward
- Model limits still apply: each box only accepts the reference types
its model supports, and existing slot/duration caps are unchanged
BFlat
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