refactor: remove dead code and commented-out tests from escrow and ev…

[Oluwasuyi-Timilehin]

#closes #366

PR Title

chore: remove dead code and unused imports for #366

PR Description

Summary

This PR fully completes issue #366 by performing a focused codebase cleanup in the TeachLink contract:

• identified and removed dead code,
• removed unused imports,
• cleaned obsolete commented-out code,
• resolved related integration test failures triggered during verification.

The scope is cleanup and stability only; no intentional feature changes were introduced.

Context

During validation, multiple integration tests in test_module_interactions.rs failed with Soroban auth errors (Error(Auth, ExistingValue)).
Root cause was duplicate authorization in role checks (auth required both at caller and inside role-check helper).
This PR includes the minimal fix to preserve behavior while making tests pass reliably.

What Changed

1) Dead Code Removal

• Removed unused result aliases from contracts/teachlink/src/errors.rs:
  • BridgeResult<T>
  • EscrowResult<T>
  • RewardsResult<T>
  • CommonResult<T>
• Removed unused helper methods from contracts/teachlink/src/provenance.rs:
  • get_creator
  • get_all_owners
• Removed associated dead-code suppression attributes in provenance.

2) Unused Imports Cleanup

• Removed unused imports from contracts/teachlink/src/events.rs:
  • PacketStatus
  • SwapStatus

3) Commented Code Cleanup

• Removed stale commented event/export sections in contracts/teachlink/src/events.rs.
• Removed large commented-out repository test block in contracts/teachlink/src/repository/escrow_repository.rs.
• Removed commented module/test/export leftovers in contracts/teachlink/src/repository/mod.rs.
• Removed large obsolete block-commented event definitions in contracts/teachlink/src/notification_events.rs.

4) Auth Stability Fix Found During Verification

• Updated contracts/teachlink/src/access_control.rs:
  • Removed require_auth() from check_role(...) to avoid duplicate auth in the same frame.
  • Added explicit caller.require_auth() in:
    • grant_role(...)
    • revoke_role(...)

This preserves authorization guarantees while preventing Auth ExistingValue panics.

Files Changed

• contracts/teachlink/src/errors.rs
• contracts/teachlink/src/events.rs
• contracts/teachlink/src/repository/escrow_repository.rs
• contracts/teachlink/src/repository/mod.rs
• contracts/teachlink/src/provenance.rs
• contracts/teachlink/src/notification_events.rs
• contracts/teachlink/src/access_control.rs
• PR_DESCRIPTION.md (updated for current PR narrative)

Why This Matters

• Reduces code noise and maintenance overhead.
• Improves readability and contributor onboarding.
• Aligns with lint cleanliness goals.
• Stabilizes cross-module tests by eliminating duplicate auth checks.

Acceptance Criteria Mapping (#366)

• Identify dead code
• Remove unused imports
• Clean up commented code
• Run linter checks
• Verify tests for impacted areas

Validation / Test Evidence

Targeted failing tests (now passing)

Previously failing tests:

• test_chain_specific_pause_isolation
• test_emergency_pause_and_resume_state_management
• test_liquidity_pool_affects_bridge_fee
• test_emergency_state_alongside_packet_operations
• test_error_propagation_across_modules
• test_multichain_config_and_packet_workflow
• test_notification_alongside_bridge_operations
• test_proposal_vote_then_bridge_completion

After auth fix in access_control, all above were re-run and passed.

Suggested verification commands

git status --short
git diff -- contracts/teachlink/src/errors.rs \
  contracts/teachlink/src/events.rs \
  contracts/teachlink/src/repository/escrow_repository.rs \
  contracts/teachlink/src/repository/mod.rs \
  contracts/teachlink/src/provenance.rs \
  contracts/teachlink/src/notification_events.rs \
  contracts/teachlink/src/access_control.rs
rg "allow\(dead_code\)" contracts/teachlink/src
cargo fmt --all -- --check
cargo clippy --all-targets --all-features -D warnings
cargo test --test test_module_interactions -- --nocapture

Risk Assessment

• Risk level: Low to Medium
• Reason: Mostly cleanup-only deletions; one targeted auth-flow correction in RBAC helper behavior.
• Mitigation: Integration tests covering bridge/emergency/message-passing flows pass after change.

Breaking Changes

None intended.

Notes for Reviewers

• Focus review on access_control auth semantics (check_role, grant_role, revoke_role) and integration-test behavior around emergency + bridge flows.
• Cleanup changes are deletion-only and should be straightforward to validate by diff.

#closes

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