feat: evm profile (Updated) (WIP)

[WaDadidou]

Based on #908
I created this PR to keep the 908 intact.

I updated with main branch.
I added docs and TODOs and added guards to avoid blocking the user (Making this EVM implementation silent)
Mostly done with Claude Code, it's a test.

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EVM Profile Integration - Exploration Branch

This branch explores storing Zenao user profiles on EVM-compatible blockchains alongside the existing backend.

Architecture: Hybrid Backend + Blockchain

Profile reads: Backend first → EVM fallback if no data
Profile writes: Backend (always) + Blockchain (optional, if configured)

Smart Contracts Required

1. Profile Contract - Stores profile data on-chain

• get(address, key) - Read a profile field
• getBatch(addresses[], keys[]) - Batch read multiple fields
• set(key, value) - Write a profile field (transaction)
• setBatch(keys[], values[]) - Batch write multiple fields (transaction)

Keys: pfp (avatar), dn (display name), bio (IPFS CID)

2. UserRegistry Contract - Maps Clerk userId ↔ wallet address (1:1)

• linkWallet(userId) - Link caller's wallet to userId
• getWallet(userId) - Get wallet for a userId
• getUserId(wallet) - Get userId for a wallet

Current State

Implemented:

• Web3Auth integration with Clerk authentication
• Hybrid query system (backend + EVM)
• Profile write to blockchain (optional, conditional on env vars)
• Wallet/userId verification on connect
• Smart contract ABIs defined
• Complete Solidity contracts in docs/EVM_SMART_CONTRACTS.md

Not yet deployed:

• Smart contracts (need deployment to testnet/mainnet)
• Environment variables (placeholders in .env.example)

To Activate

1. Deploy both smart contracts to a testnet (Optimism Sepolia or Base Sepolia recommended)
2. Configure in .env.local:
   • NEXT_PUBLIC_EVM_RPC - RPC endpoint (e.g., Alchemy)
   • NEXT_PUBLIC_EVM_PROFILE_CONTRACT_ADDRESS - Profile contract address
   • NEXT_PUBLIC_EVM_USER_REGISTRY_ADDRESS - UserRegistry contract address
3. Users must link their wallet to their userId via UserRegistry contract

Compatibility

Fully backward compatible: App works normally using only the backend if EVM env vars are not configured.

TODOs

• Deploy smart contracts to testnet
• Test profile creation/updates on-chain
• Optimize: only update changed fields instead of all 3 keys
• Add UI for wallet linking
• Production deployment strategy

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[n0izn0iz]

@WaDadidou #908 (comment)