docs(changelog): update changelog with comprehensive unreleased features and breaking changes (closes #339)

[rupesh-kumar-sah]

Overview

Closes #339.

Updates CHANGELOG.md following Keep a Changelog and SemVer standards, documenting all contract changes, security upgrades, breaking change mitigations, and new feature surfaces added to the workspace.

Summary of Documented Changes

• Role-Based Admin Access Control: Multi-admin architecture with granular AdminRole variants and delayed admin transfer (test: admin role separation, batch operations, allowance cleanup, error handling #369, feat: progress export, multi-admin support, contract upgrade mechanism, and gas estimation (#211, #212, #213, #214) #371).
• Governance & Token Vesting: VestingSchedule data structures with cliff enforcement, linear distribution curves, and governance proposal voting (feat: governance voting, token vesting, permit gasless approval, and … #366, Feature/tests pause vesting admin content hash #384).
• Contract Upgradeability: Timelocked wasm upgrade entrypoint with hash verification and security checks (learn-token: contract upgrade mechanism, claim gas estimation, event indexing, allowance cleanup #362, feat: progress export, multi-admin support, contract upgrade mechanism, and gas estimation (#211, #212, #213, #214) #371).
• Emergency Pause Controls: Contract-wide pause and unpause mechanisms with event emission (feat: course content hash, per-address minting, claim history, pause events #363, Feature/tests pause vesting admin content hash #384).
• SEP-41 Token Burning & Supply Caps: burn() / burn_from() entrypoints, configurable max_supply, and max_supply_updated event (feat: add governance to set_max_supply, max_supply_updated event, metadata_uri validation, and vitest configs #368).
• Simulation & Gas Estimation: preview_claim_reward() and estimate_claim_gas() helpers for pre-flight off-chain simulation (learn-token: contract upgrade mechanism, claim gas estimation, event indexing, allowance cleanup #362, feat: progress export, multi-admin support, contract upgrade mechanism, and gas estimation (#211, #212, #213, #214) #371).
• Batch Operations: submit_quiz_scores_batch() in progress-tracker and batch claim reward processing (feat: progress export, multi-admin support, contract upgrade mechanism, and gas estimation (#211, #212, #213, #214) #371, feat(progress-tracker): versioning, batch operations, and progress delegation #372).
• Content Integrity Verification: enroll_checked() entrypoint verifying course content SHA-256 hashes on enrollment (feat: course content hash, per-address minting, claim history, pause events #363, Feature/tests pause vesting admin content hash #384).
• Prerequisites & Course Versioning: Module prerequisite chains, course versioning, quiz retake policies, and learner completion metrics (feat(progress-tracker): prerequisites, learner stats, completion percentage, quiz retakes #364, feat: add course versioning, credential display properties, and metadata update (#246, #245, #244, #243) #376).
• Soulbound Rejection Enforcement: Explicit typed ContractError::Soulbound (1) on credential transfer() calls (Soulbound transfer rejection, delayed admin transfer, init check, and storage-size tracking #374, fix: reject credential transfer with a typed error, plus several build-blocking bug fixes #378).
• Security & Invariant Test Suite: End-to-end unit and integration suites covering arithmetic underflow/overflow, reentrancy guards, double-spending attacks, and authorization boundaries (test(learn-token): add security tests for overflow/underflow protection #379, test: add security, gas benchmark, cross-contract, and event emission tests (#286, #287, #288, #289) #383, Add security tests for unauthorized access to all admin functions #386).
• Developer Documentation: Deployment guide (docs/deployment-guide.md), troubleshooting manual (docs/troubleshooting.md), testing guide (docs/testing-guide.md), and contributor guidelines (CONTRIBUTING.md).