Reality declaration for invoice visual-test recipient mock

[marassteiner]

Context

Follow-up from review of #1274 (filed as follow-up rather than a hard block — see uncertainty below).

PR #1274 introduces installRecipientRoute in e2e/invoice-screen.spec.ts, which intercepts GET /v1/paymentLink/recipient and fulfills 200/404 JSON for visual baselines.

Evidence

• Fake: e2e/invoice-screen.spec.ts (installRecipientRoute, ~lines 16–38)
• origin/develop CONTRIBUTING.md (Reality declaration): a PR that introduces a fake must update the declaration with what a green run does not prove
• Handbook metadata notes a stubbed API (scripts/handbook/metadata.json invoice-screen entry) but is not a formal reality-declaration entry
• Taxonomy/format is owned by DFXswiss/api docs/test-architecture.md and is not fully specified inside this repository

Uncertainty

Develop already ships many e2e/** page.route mocks without per-mock declaration entries (visual layer does not run in CI). Whether each new visual-route mock needs its own declaration entry, or only full-stack harness fakes, should be confirmed against the API taxonomy doc before treating this as incomplete.

Suggested work

After confirming the expected location/format:

1. Add the declaration entry stating that green visual invoice runs do not prove real recipient resolution or the SDK/API contract
2. Link it from docs/test-architecture.md if that is the services-side stamp