feat: show copied layer origin in paste tooltip

[mondalaci]

Summary

• Store device, keymap, and layer names when a layer is copied to the virtual clipboard
• Update the paste button tooltip to show the copied layer's origin (e.g. My UHK: QWERTY: Mod)

Test plan

• Copy a layer on a keymap and hover the paste button — tooltip shows the correct device, keymap, and layer names
• Switch to a different keymap/layer and paste — tooltip still shows the origin layer, not the current one
• Copy a different layer — tooltip updates to the new origin

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