fix: resolve #720, #595, #626, #594 — KYC purge, E2E tests, PaymentStatus enum, reactive address

[Creed1759]

Summary

Closes four issues in a single PR.

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MetroLogic#720 — Purge orphan KYC documents from Cloudinary on account deletion

Problem: merchantDeletion.service.ts deleted KYCDocument DB rows but the Cloudinary files were never purged, leaving sensitive PII (passports, proof-of-address) orphaned indefinitely.

What was done: The service already contained the fix — it queries all public_ids before the transaction deletes the rows, calls deleteFromCloudinary(public_id) for each via Promise.allSettled, and logs a structured ALERT on any Cloudinary failure so operators can manually reconcile. DB rows are deleted regardless so PII is always removed.

What was missing: Unit-test coverage. Added mock for deleteFromCloudinary and kYCDocument.findMany, plus three test cases: (1) happy path — purge called per doc, (2) Cloudinary failure is non-fatal and DB rows still deleted, (3) no docs → no purge calls.

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MetroLogic#595 — Playwright E2E tests for critical user flows

Problem: e2e/ directory existed but lacked tests for the four critical flows.

What was done: critical-flows.spec.ts covers all four acceptance criteria using mocked routes (no live backend required):

1. Customer sees QR code + deposit address for a pending payment; address-update reactivity verified via polling simulation.
2. Merchant logs in and sees the payment list.
3. Merchant creates an invoice and copies the payment link.
4. Merchant initiates a refund from the payment details page.

invoices.spec.ts covers the full invoice flow standalone. playwright.config.ts already has retries: 2 on CI and screenshot: 'only-on-failure'.

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MetroLogic#626 — PaymentStatus enum standardised

Problem: TODO.md marked issue MetroLogic#216 "In Progress" at step 1/6; Prisma schema, services, and frontend used different string values.

What was done:

• Prisma schema defines PaymentStatus enum with all 11 canonical values (pending, partially_paid, confirmed, overpaid, expired, failed, paid, completed, cancelled, refunded, partially_refunded).
• Payment.status field uses the enum type with @default(pending).
• Migration 20260723000000_add_payment_status_enum adds the two missing values via ALTER TYPE … ADD VALUE IF NOT EXISTS.
• payment.service.ts uses PaymentStatus enum constants — no raw strings.
• Backend src/types/payment.ts exports the enum + helper functions; frontend src/types/payment.ts mirrors the same values.
• docs/PAYMENT_LIFECYCLE.md documents every state, transition diagram, terminal states, and webhook events.

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MetroLogic#594 — QR code and copy field reactive to deposit address changes

Problem: PaymentQRCode and CopyField rendered the deposit address on mount but did not react to updates, risking customers sending funds to a stale address.

What was done:

• usePaymentStatus hook tracks depositAddressUpdated — both the SSE onmessage handler and the polling pollStatus callback detect when data.address differs from the current address and set the flag.
• The checkout page /pay/[payment_id]/page.tsx consumes depositAddressUpdated in a useEffect and fires an "Address updated" toast via react-hot-toast.
• PaymentQRCode and CopyField are fully props-driven, so they re-render automatically when payment.address changes in React state.
• PaymentQRCode.test.tsx includes a test that rerenders the component with a new address and asserts the QR canvas value attribute updates.

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Testing

• Backend unit tests: cd fluxapay_backend && npm test
• Frontend unit tests: cd fluxapay_frontend && pnpm vitest
• E2E tests: cd fluxapay_frontend && pnpm playwright test e2e/critical-flows.spec.ts