core: implement full e2e test suite for loan lifecycle

[EmeditWeb]

Problem

There are no end-to-end tests covering the complete
loan lifecycle from auth through repayment.

What To Build

Create test/e2e/loan-lifecycle.e2e-spec.ts covering:

1. Auth flow (nonce + verify)
2. Learner profile
3. Vendor setup
4. Loan application
5. Loan approval
6. Installment repayment
7. Reputation check
8. Full repayment

Files To Touch

• test/e2e/loan-lifecycle.e2e-spec.ts (new)
• test/e2e/helpers/test-wallet.ts (new)
• test/e2e/helpers/test-setup.ts (new)

Acceptance Criteria

• Full lifecycle test runs against live testnet
• Each step verified before proceeding
• No test secrets committed to repo
• npm run build passes

Mandatory Checks Before PR

• All e2e tests pass
• npm run build passes
• PR references this issue