feat: add end-to-end test suite

[Faromzy]

feat: add end-to-end test suite

Adds a comprehensive end-to-end test suite (tests/test_e2e.rs) covering
complete workflows, cross-module integrations, user scenarios, and output
validation.
Tests added (12 total):

• e2e_bridge_init_and_validator_workflow — bridge initialization,
  validator/chain management, fee config
• e2e_bft_consensus_workflow — validator registration, proposal creation,
  voting, consensus reached
• e2e_rewards_lifecycle — fund pool, set rates, issue rewards, claim, verify
  balances
• e2e_content_tokenization_and_provenance — mint NFT, transfer ownership,
  provenance chain integrity
• e2e_assessment_full_workflow — create questions, submit answers, verify
  grading output
• e2e_user_learning_journey — participation → course completion → contribution
  → credit score
• e2e_emergency_pause_resume — pause/resume bridge and individual chains
• e2e_atomic_swap_workflow — initiate swap, accept with preimage, verify
  completion
• e2e_audit_and_compliance_workflow — create audit records, generate compliance
  report
• e2e_interface_versioning_workflow — set versions, query status, compatibility
  checks
• e2e_multi_content_token_output_validation — mint multiple content types,
  verify IDs and ownership
• e2e_backup_and_recovery_workflow — create backup, verify integrity, schedule,
  record recovery

Changes:

• contracts/teachlink/tests/test_e2e.rs — new test file
• contracts/teachlink/Cargo.toml — registered test_e2e as a named test target
  closes Add end-to-end test suite #347

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[Xhristin3]

@Faromzy fix the CI.