feat(cli): image pasting support via Ctrl+V and /paste command

[Stranmor]

Closes #2811

This PR adds support for inserting images directly into the chat prompt from the clipboard.

Features

• Binds Ctrl+V in the prompt to read an image from the clipboard.
• Adds /paste slash command as an alternative way to paste images.
• Images are saved as PNG in ~/.local/share/forge/images and inserted as @[/path/to/image.png].
• Implements a robust clipboard fetching fallback:
  1. Tries native Wayland/X11 tools (wl-paste, xclip) for accurate pixel extraction.
  2. Falls back to arboard if native tools aren't present.
  3. Checks if the clipboard contains file URIs (file://...) or absolute paths if the user copied image files directly from a file manager.

[CLAassistant]

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