fix: add warning styling to contract address display

The contract address in AddressToken view was visually indistinguishable
from the wallet address, creating a risk of users sending funds to the
contract address. Changes:

- Red warning border around contract info section
- Warning icon and 'DO NOT send funds to this address' label
- Muted text color for the contract address itself
- Updated README.md with documentation on the safety treatment

README.md

@@ -335,6 +335,14 @@ transitions.
     - Full address (color dot, etherscan link, tap to copy)
     - USD total for this token
     - Single token balance line (4 decimal places)
+    - Token contract info (ERC-20 only): displayed for informational and
+      verification purposes only. Styled with a red warning border, ⚠️ icon, and
+      explicit "DO NOT send funds to this address" label to prevent users from
+      confusing the contract address with their wallet address. The contract
+      address itself is rendered in muted text. This distinction is critical
+      because funds sent to a token contract address are typically
+      irrecoverable. The Etherscan link and click-to-copy functionality are
+      preserved for verification use.
     - Send / Receive buttons
     - Token-filtered transaction list (only this token's transfers)
 - **Transitions**: