feat(web3): Automated Proof of Delivery (PoD) NFT Minting & Recipient Claims

[hrshjswniii]

📌 Overview

This PR implements [feature] : Automated Proof of Delivery (PoD) NFT Minting & Recipient Claims enabling digital cryptographic ERC-721 Proof of Delivery certificates containing IPFS provenance metadata (harvest origin, temperature history, inspection hash) to be automatically minted or claimed by recipients upon final batch delivery.

Key Changes Introduced:

1. Smart Contracts Architecture:
   • Updated [ProofOfDeliveryNFT.sol] with claimProofOfDelivery(bytes32 batchId, string calldata metadataURI) and getProofByBatch(bytes32 batchId) view helper.
2. Backend Service & Route Integration:
   • Created [backend/services/podService.js] generating IPFS metadata payloads.
   • Updated [backend/routes/batchRoutes.js] with GET /api/batches/:id/pod-nft.
3. Automated Unit Test Suite:
   • Created [smart-contracts/test/proofOfDeliveryNFT.test.js] testing mintProof(), claimProofOfDelivery(), duplicate token prevention, and owner balances (3/3 tests passing).

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🛠️ Type of Change

• ⛓️ Smart Contract (Solidity changes, ERC-721 NFT, AccessControl)
• 💻 Frontend (UI/UX, React components)
• ⚙️ Backend (API routes, Web3 metadata service)
• 📄 Documentation (README, Roadmap updates)
• 🧪 Testing (Hardhat unit tests)

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🔗 Related Issue

Closes #1306

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🧪 Testing & Verification

• Smart Contracts: npx hardhat test test/proofOfDeliveryNFT.test.js passed? (Yes) — 3/3 tests passing in 3s.
• Backend: GET /api/batches/:id/pod-nft metadata formatting verified? (Yes).

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✅ PR Checklist

• My code follows the project's style guidelines.
• I have commented my code, particularly in complex areas (e.g., token ID mapping & IPFS metadata formatting).
• I have updated the documentation accordingly.
• My changes generate no new warnings.

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💬 Additional Notes

• Updated [smart-contracts/contracts/ProofOfDeliveryNFT.sol]
• Created [smart-contracts/test/proofOfDeliveryNFT.test.js]
• Created [backend/services/podService.js]
• Updated [backend/routes/batchRoutes.js]

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