feat: comprehensive integrations and upgrades for #112, #113, #77, #69

[walterthesmart]

This PR addresses and resolves the following issues by introducing several new integration modules and major feature upgrades to the PropChain-contract ecosystem:

Resolved Issues

• Closes Insufficient Database Integration #112: Off-Chain Database Integration
• Closes Missing Third-Party Service Integration #113: Third-Party Service Integrations (KYC, Payments, Monitoring)
• Closes Lack of Contract Upgrade Strategy #77: Enhanced Contract Upgrade Strategy (Governance, Timelocks, Rollback)
• Closes Implement Advanced Property Metadata Standard #69: Advanced Property Metadata Standard (IPFS, Multimedia, Legal Docs)

Tasks Performed & Fixes Made

1. Database Integration (#112)

• Implemented propchain-database crate acting as the on-chain coordination layer for off-chain databases.
• Introduced reliable DataSyncEvent emission for property, transfer, escrow, token, and valuation states.
• Added data export batch processing capabilities for external indexers.
• Implemented robust sync verification endpoints to confirm indexer integrity off-chain.
• Integrated analytics snapshots mapping (total valuation, totals, accounts).

2. Third-Party Service Integration (#113)

• Implemented propchain-third-party crate to orchestrate external calls/integrations safely securely.
• Introduced KYC/AML integration with request matching, status updates, and lifecycle verification flows.
• Added Fiat Payment Gateway wrappers to facilitate fiat-to-token operations securely and seamlessly.
• Enabled off-chain system monitoring and alerting logs directly through contract state events.
• Created robust provider management mechanisms allowing admin assignment and rotation of multiple external agencies securely.

3. Contract Upgrade Strategy & Governance (#77)

• Completely rewrote the existing proxy contract transparent-proxy implementation.
• Established a Multi-Sig Upgrade Governance mechanism for logic contract deployments.
• Implemented upgrade "timelocks" to create a delay period before the payload is executable.
• Built explicit version compatibility checking for upgrade implementations securely guaranteeing schema consistency.
• Introduced a transparent rollback mechanism for safely restoring logic payloads to the previous version history.
• Built a Migration State machine enabling clear tracing of execution (Proposed -> Approved -> InProgress -> Completed).

4. Advanced Property Metadata Standard (#69)

• Re-architected schema in the propchain_metadata crate offering extensive typing.
• Introduced versioned IPFS Integration specifically delineating documents_cid, images_cid, legal_docs_cid, virtual_tour_cid.
• Implemented native multimedia representation (Images, Videos, Virtual Tours, Floor Plans).
• Provided verification mechanisms for distinct embedded Legal Documents natively on-chain.
• Added support for dynamic & custom attribute Key-Value associations to represent esoteric and custom external properties natively.

Note: The PR exclusively consists of code and necessary dependencies, and intentionally refrains from pushing .wasm artifacts or build footprints, adhering to repository guidelines.

Summary by CodeRabbit

Release Notes

• New Features
  • Introduced database synchronization contract with event tracking, analytics snapshots, and data export management capabilities.
  • Launched advanced property metadata registry supporting versioning, multimedia content, and legal document handling.
  • Added third-party service integration layer featuring KYC workflows and fiat payment processing.
  • Enhanced proxy contract with governance-based upgrade proposals, version tracking, and emergency rollback functionality.

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