Implement Receive Asset Screen with QR Code and Copy Address [Flutter] #51
Description
Build the Receive screen that displays a QR code for the user's wallet address. Below the QR code, show Network (with icon), Asset (with icon), and full wallet Address with a copy icon. A "Share address" button at the bottom opens the native share sheet. Include a warning banner at the top: "Send only [ASSET] via the [NETWORK] network. Using any other asset or network will result in permanent loss." When the copy icon is tapped, show a toast/snackbar: "Wallet address copied to clipboard."
Acceptance Criteria:
- QR code is generated from the user's wallet address and renders correctly
- Warning banner displays asset and network as tappable/highlighted text
- Network, Asset, and Address fields are shown below the QR code
- Copy icon next to the address copies the address to clipboard
- Toast/snackbar "Wallet address copied to clipboard." appears after copying
- "Share address" button triggers the native share sheet with the wallet address
- "Need Help?" button is visible in the top-right corner