feat(VFileUpload): add allowPaste prop to support pasting files from clipboard

[mixelburg]

Fixes #22732

Problem

There's no way to paste files (e.g. screenshots) directly into VFileUpload. Users have to paste into an image editor first, save the file, then drag-and-drop or browse for it.

Solution

Added an allowPaste boolean prop. When enabled, a paste event handler intercepts ClipboardEvent.clipboardData.files and passes them through the existing selectAccepted() flow — same path used by drag-and-drop and file browse selection.

<v-file-upload allow-paste multiple />

Users can now Ctrl+V / Cmd+V anywhere on the page when the component is focused to add files.

Implementation notes

• Uses the same selectAccepted() path as drag-drop → file type filtering and rejected events work as expected
• allowPaste defaults to false → fully backward-compatible
• Guard: no-op when disabled is set
• No paste handler is attached at all when allowPaste is false (no unnecessary event listener)

[J-Sek]

1. read Docs » contributing » choosing-a-base-branch
2. switch target to dev
3. should support pasting folders