feat: USDC Escrow for external email payments

- PaymentEscrow.sol: deposit/release/refund with 0.10 USDC minimum
- Deployed to Base Mainnet: 0x220bdbd8fb5e908eb04b66f32bf6ecb29b92d60b
- Worker: /api/claim/:id (GET info, POST claim with auth)
- Worker: /api/send supports escrow_claim param for external emails
- Frontend: /claim/:id page (connect wallet → register → claim → receipt)
- DB: escrow_claims table with auto-migration
- Claim flow: forces BaseMail account creation, delivers receipt as internal email
- Rollback: all additive, git revert one commit

Author: CloudLobster

contracts/build/contracts_PaymentEscrowFlat_sol_Address.abi

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+[]

contracts/build/contracts_PaymentEscrowFlat_sol_Address.bin

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+6055604b600b8282823980515f1a607314603f577f4e487b71000000000000000000000000000000000000000000000000000000005f525f60045260245ffd5b305f52607381538281f3fe730000000000000000000000000000000000000000301460806040525f80fdfea264697066735822122070cd9d4b8b8aad99c43184dc7fd3ca8240bff6535c86cbfd56943e4125eb44a564736f6c634300081a0033

contracts/build/contracts_PaymentEscrowFlat_sol_IERC20.abi

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+[{"inputs":[{"internalType":"address","name":"owner","type":"address"},{"internalType":"address","name":"spender","type":"address"}],"name":"allowance","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"spender","type":"address"},{"internalType":"uint256","name":"value","type":"uint256"}],"name":"approve","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"account","type":"address"}],"name":"balanceOf","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"totalSupply","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"value","type":"uint256"}],"name":"transfer","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"from","type":"address"},{"internalType":"address","name":"to","type":"address"},{"internalType":"uint256","name":"value","type":"uint256"}],"name":"transferFrom","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"nonpayable","type":"function"}]

contracts/build/contracts_PaymentEscrowFlat_sol_IERC20.bin

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+[{"inputs":[{"internalType":"address","name":"_usdc","type":"address"}],"stateMutability":"nonpayable","type":"constructor"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"bytes32","name":"claimId","type":"bytes32"},{"indexed":true,"internalType":"address","name":"sender","type":"address"},{"indexed":false,"internalType":"uint256","name":"amount","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"expiry","type":"uint256"}],"name":"Deposited","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"oldOwner","type":"address"},{"indexed":true,"internalType":"address","name":"newOwner","type":"address"}],"name":"OwnerChanged","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"bytes32","name":"claimId","type":"bytes32"},{"indexed":true,"internalType":"address","name":"sender","type":"address"},{"indexed":false,"internalType":"uint256","name":"amount","type":"uint256"}],"name":"Refunded","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"bytes32","name":"claimId","type":"bytes32"},{"indexed":true,"internalType":"address","name":"claimer","type":"address"},{"indexed":false,"internalType":"uint256","name":"amount","type":"uint256"}],"name":"Released","type":"event"},{"inputs":[],"name":"MIN_AMOUNT","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"bytes32","name":"claimId","type":"bytes32"},{"internalType":"uint256","name":"amount","type":"uint256"},{"internalType":"uint256","name":"expiry","type":"uint256"}],"name":"deposit","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"bytes32","name":"","type":"bytes32"}],"name":"deposits","outputs":[{"internalType":"address","name":"sender","type":"address"},{"internalType":"uint256","name":"amount","type":"uint256"},{"internalType":"uint256","name":"expiry","type":"uint256"},{"internalType":"bool","name":"settled","type":"bool"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"bytes32","name":"claimId","type":"bytes32"}],"name":"getDeposit","outputs":[{"internalType":"address","name":"sender","type":"address"},{"internalType":"uint256","name":"amount","type":"uint256"},{"internalType":"uint256","name":"expiry","type":"uint256"},{"internalType":"bool","name":"settled","type":"bool"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"owner","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"bytes32","name":"claimId","type":"bytes32"}],"name":"refund","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"bytes32","name":"claimId","type":"bytes32"},{"internalType":"address","name":"claimer","type":"address"}],"name":"release","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"newOwner","type":"address"}],"name":"transferOwnership","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[],"name":"usdc","outputs":[{"internalType":"contract IERC20","name":"","type":"address"}],"stateMutability":"view","type":"function"}]

contracts/build/contracts_PaymentEscrowFlat_sol_PaymentEscrow.abi

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contracts/build/contracts_PaymentEscrowFlat_sol_PaymentEscrow.bin

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+[]

contracts/build/contracts_PaymentEscrowFlat_sol_SafeERC20.abi

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