feat(e2e): add configurable Playwright tests for localhost API

[TaprootFreak]

Summary

• Make auth-cache.ts API URL configurable via E2E_API_URL environment variable
• Add playwright.local.config.ts for running tests against localhost:3000
• Add refund-creditor-data.spec.ts with 5 comprehensive E2E tests for bank refund flow
• Add visual regression baseline and test screenshots

Tests included

1. should load refund page for a failed transaction - Verifies refund page loads correctly
2. should display refund details and creditor form - Checks all form fields are present
3. should fill creditor data and submit refund request - Tests form filling flow
4. visual regression - refund page - Screenshot comparison for UI consistency
5. should show transaction list with refund option - Verifies transaction list rendering

Usage

# Create .env.test.local with:
E2E_API_URL=http://localhost:3000/v1
TEST_TX_ID=T11  # or your transaction UID

# Run tests
npx env-cmd -f .env.test.local npx playwright test --config=playwright.local.config.ts

Test plan

• All 5 tests pass against localhost:3000 API
• Visual regression baseline created
• Screenshots captured for documentation

[TaprootFreak]

Superseded by #838 and #839. The refund UI no longer has creditor input fields, so these tests are obsolete.