Read QR codes in clipboard manager, auto-tag URLs as Links

When an image is copied to the clipboard, decode any QR codes in it. If the QR content is a URL, tag the entry as a Link so the user can click straight through to it from the clipboard history. Bonus territory: WiFi QR (connect to network), vCard QR (add contact), plain text QR (store as text). Decoding stays fully local via rqrr crate.