fix: safe status-recommendation flow, MO-016 order independence, brand constant, message codes

- Add a single shared, pure vehicle-status evaluator (app/services/vehicle_status.py)
  used identically by the data-quality scanner, a new non-mutating status-recommendation
  preview endpoint, and a transactional apply endpoint with optimistic-concurrency token
  revalidation -- eliminates the old opaque "calculate and apply" action and the unsafe
  "maintenance + active booking -> auto rented" shortcut. Frontend
  DataQualityIssueDetail.tsx now shows a review/decide/confirm panel with localized
  why/evidence/consequence text in nl-BE/en-GB/fr-BE, with an exact "Change status to
  <status>" confirm action per the brief.
- Fix MO-016 issue-order dependency: resolving the booking-overlap issue before vs.
  after the status-conflict issue now converges on the same final vehicle status,
  proven by test_mo_016_status_conflict_recommendation_is_order_independent.
- Make "Fleet Ops" a non-localizable brand constant (frontend/src/product.ts,
  backend PRODUCT_NAME) via {{productName}} interpolation everywhere the brand name
  appeared in locale prose; add a permanent test guarding against a translation file
  ever defining the brand name or an "appName" key again.
- Convert dynamic backend prose to stable message codes + params: return status
  reasons, audit field/actor-type labels, automation last_error, and search
  section/vehicle/booking/issue results all now carry codes the frontend localizes,
  with raw technical text demoted to a "Technical details" disclosure.
- docs/fleet-ops-correction/: gap audit, i18n inventory, and the vehicle-status
  decision table documenting the evaluator's rules and safe-status principles.

148 backend tests + Ruff + mypy green; Alembic migration verified upgrade/downgrade;
frontend tsc/build and the i18n-coverage Playwright suite green.

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

frontend/src/i18n/locales/nl-BE/auth.json

@@ -3,7 +3,7 @@
   "orgLine": "Demo-organisatie: {{orgName}} (fictief)",
   "headline1": "Elke overdracht.",
   "headline2": "Eén helder overzicht.",
-  "defaultDescription": "Fleet Ops brengt voertuig-, boekings- en operationele gegevens samen, ondersteunt verhuurprocessen, detecteert datakwaliteitsproblemen en automatiseert gecontroleerde vervolgstappen.",
+  "defaultDescription": "{{productName}} brengt voertuig-, boekings- en operationele gegevens samen, ondersteunt verhuurprocessen, detecteert datakwaliteitsproblemen en automatiseert gecontroleerde vervolgstappen.",
   "footnote": "Synthetische demo · geen echte klant- of voertuiggegevens · op elk moment herstelbaar",
   "accessEyebrow": "Demo-toegang",
   "accessHeading": "Kies hoe je wil starten",