feat: implement release readiness checklist (Issue #50)

[ExcelDsigN-tech]

Closes #100

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Implement release readiness checklist (Issue #100)

Overview

This PR implements an on-chain Release Readiness Checklist for the TalentTrust escrow contract ecosystem. Moving beyond manual verification, this system enforces deployment, verification, and post-deploy monitoring gates directly within the smart contract logic. Phase 1 gates are strictly enforced; the release_milestone operation is hard-blocked until all pre-deployment conditions are satisfied, ensuring contract integrity and fund security.

Feature Summary

• Automated On-Chain Gates: Implements a 3-phase checklist (Pre-deploy, Release Gate, Post-deploy) where status is updated automatically by contract state transitions.
• Strict Enforcement: Integrated ChecklistIncomplete error handling that prevents milestone releases if core requirements (authentication, milestone definition, and fund deposit) are not met.
• Persistent Storage Architecture: New DataKey and EscrowData structures to manage complex lifecycles and state isolation between multiple independent contracts.
• Safety Guards: Implementation of MAX_MILESTONES constants to prevent storage bloat and unbound gas costs.

Technical Implementation

The implementation refactors contracts/escrow/src/lib.rs to replace stub logic with a robust state machine. We introduced the ReleaseChecklist struct to track 6 distinct boolean gates. Key technical shifts include:

1. Error Handling: A comprehensive EscrowError enum with 6 typed codes for granular failure reporting.
2. Storage Pattern: Transitioned to a persistent storage model using DataKey to manage contract metadata, checklist status, and ID incrementing.
3. State Logic: Public getters get_release_checklist and is_release_ready allow off-chain UI and monitoring tools to query readiness without dry-running transactions.
4. Validation: Added internal validation checks for InvalidDepositAmount and TooManyMilestones to harden the create_contract and deposit_funds flows.

Test Coverage

• Comprehensive Suite: Expanded from 4 to 23 tests in contracts/escrow/src/test.rs.
• Failure Path Analysis: Verified all 6 error codes, specifically testing for ChecklistIncomplete (Error 4) and InvalidMilestoneId.
• State Isolation: Confirmed that independent contracts maintained unique checklist states without collision.
• Documentation: Created release-readiness-checklist.md and updated the root README.md with phase tables and security models.

Tasks

• Implement ReleaseChecklist and EscrowData structs in lib.rs
• Integrate checklist auto-update logic into create_contract and deposit_funds
• Apply ChecklistIncomplete panic gate to release_milestone
• Write 23 unit/integration tests covering happy and failure paths
• Update README.md and generate docs/escrow/release-readiness-checklist.md
• Configure .gitignore for Soroban test snapshots and coverage reports

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[mikewheeleer]

resolve the conflicts

[ExcelDsigN-tech]

resolve the conflicts
Merge conflicts resolved

[mikewheeleer]

@ExcelDsigN-tech Resolve the conflicts

[ExcelDsigN-tech]

@mikewheeleer All merge conflicts has been resolved