docs(api): correct /docs/api against the v1 implementation (#999)

Audited every endpoint, param, header, request/response field, error code, and
webhook event in the public API docs against the v1 implementation and fixed the
drift; addressed two rounds of CodeRabbit review.

- Error envelope, idempotency, dry-run, and reversal-field corrections.
- Registered the missing articles/dimensions/inbox-items reference resources.
- Cookbook fixes: removed nonexistent endpoints, corrected params/fields, fixed
  the test-key vs live-key quickstart flow and the year-end lock/close sequence.
- Webhooks/changelog: retry window ~87h (incl. route metadata), shipped-vs-
  coming-soon, counts, API-key format, previous_attributes.
- export-docs-to-website.mts absolutises app-served links for the website.

The gnubok-website side is on branch docs/api-correctness (already deployed).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

lib/docs/nav.ts

@@ -57,6 +57,7 @@ export const DOCS_NAV: DocsNavSection[] = [
       { label: 'Companies', href: '/docs/api/reference/companies' },
       { label: 'Customers', href: '/docs/api/reference/customers' },
       { label: 'Invoices', href: '/docs/api/reference/invoices' },
+      { label: 'Articles', href: '/docs/api/reference/articles' },
       { label: 'Suppliers', href: '/docs/api/reference/suppliers' },
       { label: 'Supplier invoices', href: '/docs/api/reference/supplier-invoices' },
       { label: 'Transactions', href: '/docs/api/reference/transactions' },
@@ -64,6 +65,8 @@ export const DOCS_NAV: DocsNavSection[] = [
       { label: 'Fiscal periods', href: '/docs/api/reference/fiscal-periods' },
       { label: 'Accounts', href: '/docs/api/reference/accounts' },
       { label: 'Documents', href: '/docs/api/reference/documents' },
+      { label: 'Inbox items', href: '/docs/api/reference/inbox-items' },
+      { label: 'Dimensions', href: '/docs/api/reference/dimensions' },
       { label: 'Employees', href: '/docs/api/reference/employees' },
       { label: 'Salary runs', href: '/docs/api/reference/salary-runs' },
       { label: 'Reports', href: '/docs/api/reference/reports' },