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>

backend/app/services/returns.py

@@ -28,19 +28,41 @@ def _next_public_ref(db: Session) -> str:
 
 def _derive_vehicle_status_with_reason(
     body: RegisterReturnRequest, vehicle: Vehicle, new_odometer: int
-) -> tuple[str, str]:
+) -> tuple[str, str, dict[str, str | int]]:
+    # Stable, localizable codes + params -- the backend never emits prose here. The
+    # frontend renders review.reasonCodes.<code> in the selected locale; the mirrored
+    # raw-English fallback strings live only in status_reason (shown under "Technical
+    # details") for backward compatibility. See docs/fleet-ops-correction/i18n-inventory.md.
     if body.damage_reported and body.technical_warning:
-        return "blocked", "Damage and a technical warning were both reported on return."
+        return (
+            "blocked",
+            "returnBlockedDamageAndTechnical",
+            {},
+        )
     if body.damage_reported:
-        return "blocked", "Damage was reported on return."
+        return "blocked", "returnBlockedDamage", {}
     if body.technical_warning:
-        return "blocked", "A technical warning was reported on return."
+        return "blocked", "returnBlockedTechnicalWarning", {}
     if new_odometer >= vehicle.next_service_km:
         return (
             "maintenance",
-            f"Odometer reached the {vehicle.next_service_km:,} km service threshold.",
+            "returnServiceThresholdReached",
+            {"threshold_km": vehicle.next_service_km},
         )
-    return "cleaning", "No damage, technical warning or service threshold; routed to cleaning."
+    return "cleaning", "returnRoutedToCleaning", {}
+
+
+_STATUS_REASON_FALLBACK_TEXT: dict[str, str] = {
+    "returnBlockedDamageAndTechnical": (
+        "Damage and a technical warning were both reported on return."
+    ),
+    "returnBlockedDamage": "Damage was reported on return.",
+    "returnBlockedTechnicalWarning": "A technical warning was reported on return.",
+    "returnServiceThresholdReached": "Odometer reached the service threshold.",
+    "returnRoutedToCleaning": (
+        "No damage, technical warning or service threshold; routed to cleaning."
+    ),
+}
 
 
 @dataclass
@@ -51,6 +73,8 @@ class ReturnEvaluation:
     resulting_odometer_km: int
     resulting_vehicle_status: str
     status_reason: str
+    status_reason_code: str
+    status_reason_params: dict[str, str | int]
     would_create_quality_issue: bool
     attention_reasons: list[str]
     next_booking_risk: dict | None
@@ -64,9 +88,10 @@ def evaluate_return(
     preview and commit can never drift apart."""
     odometer_regression = body.end_odometer_km < vehicle.odometer_km
     resulting_odometer_km = vehicle.odometer_km if odometer_regression else body.end_odometer_km
-    resulting_status, status_reason = _derive_vehicle_status_with_reason(
+    resulting_status, status_reason_code, status_reason_params = _derive_vehicle_status_with_reason(
         body, vehicle, resulting_odometer_km
     )
+    status_reason = _STATUS_REASON_FALLBACK_TEXT[status_reason_code]
 
     attention_reasons = []
     if body.damage_reported:
@@ -101,6 +126,8 @@ def evaluate_return(
         resulting_odometer_km=resulting_odometer_km,
         resulting_vehicle_status=resulting_status,
         status_reason=status_reason,
+        status_reason_code=status_reason_code,
+        status_reason_params=status_reason_params,
         would_create_quality_issue=odometer_regression,
         attention_reasons=attention_reasons,
         next_booking_risk=next_booking_risk,