Integrate Sign-In with Ethereum (SIWE) for Off-Chain User Profiles

[Lakes41]

Background

The application currently relies solely on local storage to save user preferences (theme, slippage tolerance, notification settings), which are lost if the user clears their cache or switches devices.

Problem

Without a secure off-chain authentication mechanism, there is no way to persist user preferences to a backend database tied to their wallet address.

Expected Outcome

Implementation of EIP-4361 (Sign-In with Ethereum) to establish authenticated sessions, allowing the backend to securely store and retrieve user preferences.

Suggested Implementation

• Implement SIWE message generation and signature requests in the frontend.
• Send signed messages to the /auth/verify backend endpoint to receive a JWT session token.
• Store the JWT securely in an HttpOnly cookie or memory.
• Fetch user profile settings from the backend upon successful authentication.

Acceptance Criteria

• Users are prompted to sign a standard SIWE message upon clicking "Sign In".
• Preferences persist across different browsers and devices for the same wallet address.
• Signature requests use the correct domain and URI to prevent replay attacks.

Likely Affected Files

• src/services/auth.ts
• src/hooks/useSIWE.ts
• src/components/Profile/ProfileSettings.tsx

Requirements

• The SIWE message must include a random nonce fetched from the backend to prevent replay attacks.