feat: Partner hierarchy backoffice page (F41-F44 partial)

New nav entry, route, page. Renders the four-level tree
(Company/Project/Store/PaymentPoint) via AdminPartnerHierarchyFacade on top
of the core built in the previous commit - TEST/LIVE toggle, suspend/activate,
disable behind a confirmation (terminal + cascading, per contract §2), and a
read-only credentials list stating plainly that only the public key is ever
held.

Reload-after-action rather than local patch on suspend/activate/disable:
disable cascades to descendants server-side, so a local patch would leave
children showing a status they no longer have.

Company id is a constant for now (DEFAULT_COMPANY_ID) - company creation is
out of band per contract §4.3, and there is no company-selector UI yet.

Verified: 139/139 unit tests, arch:check clean, production build succeeds.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/app/i18n/translations.ts

@@ -2067,6 +2067,7 @@ export interface Translations {
       integrations: string;
       finance: string;
       marketplaces: string;
+      partnerHierarchy: string;
       audit: string;
       reports: string;
       partnersGroup: string;