Search user via QR code

[mrsumanbiswas]

Enable quick contact discovery by scanning a QR code.

• Each user can display a QR code containing their unique user ID (or contact link)
• Other users can scan this QR code using the app’s built‑in scanner
• After scanning, the app should open the conversation (or add the contact)
• The QR code can also be shared as an image from the profile screen

Integrate a QR scanning library in Flutter; ensure camera permissions are handled gracefully.

[mrsumanbiswas]

@ChandruWritesCode qr code based username function is already there now enable a search function for the same