feat: Implement Protocol Upgradeability & Governance-Controlled Upgrade Framework (SC-034)

[akansmafengadamu]

Summary

Implements the complete Protocol Upgradeability & Governance-Controlled Upgrade Framework as specified in SC-034. This establishes a secure, transparent, and auditable upgrade architecture for the TruthBounty protocol.

Changes

New Contracts (contracts/upgrade/)

• IUpgradeController.sol - Interface for the full upgrade lifecycle
• UpgradeController.sol - Governance-controlled upgrade lifecycle manager with Standard/Emergency/Rollback types, configurable timelocks, execution windows, storage validation integration, and role-based access
• IVersionRegistry.sol - Interface for canonical version history
• VersionRegistry.sol - Maintains immutable record of every deployed version with semantic versioning
• StorageCompatibilityValidator.sol - Validates storage layout compatibility before upgrades
• ProtocolUpgradeable.sol - Abstract UUPS base contract for upgradeable protocol contracts

New Tests (test/upgrade/)

• UpgradeController.t.sol - 18 unit tests covering propose, schedule, execute, cancel, rollback, emergency, access control, pause, and timelock enforcement
• VersionRegistry.t.sol - 14 unit tests covering registration, status updates, active tracking, and errors
• UpgradeIntegration.t.sol - 10 integration tests covering full lifecycle, storage validation, and rollback flow

Architecture

Follows the existing UUPS proxy pattern. Integrates with GovernanceController and GovernanceOwnable. Uses OpenZeppelin 5.x. Compiled with Solidity ^0.8.28.

Closes #314