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/vehicle_status.py

@@ -0,0 +1,218 @@
+"""The single authoritative vehicle-status evaluator.
+
+Used by the data-quality scanner (detection), the status-recommendation preview
+endpoint, the apply endpoint, and tests -- so scan-time detection and resolve-time
+recommendation can never structurally disagree (see docs/fleet-ops-correction/
+vehicle-status-decision-table.md for the full decision table and rationale).
+
+The evaluator only ever reasons from real, freshly-queried domain facts (an actually
+active rental, a real service-threshold breach, a real overlapping-booking conflict) --
+never from a proxy like "does some other high-severity issue happen to be open". It is
+therefore also order-independent: resolving, deferring or rejecting an unrelated issue on
+the same vehicle never changes what this function returns, because it never looks at
+issue history, only at the vehicle's/bookings' current state.
+"""
+
+from __future__ import annotations
+
+import hashlib
+import json
+import uuid
+from dataclasses import dataclass, field
+
+from sqlalchemy import select
+from sqlalchemy.orm import Session
+
+from app.models.booking import Booking
+from app.models.data_quality import DataQualityIssue
+from app.models.vehicle import Vehicle
+
+# Every code below is a stable, localizable identifier -- see
+# frontend/src/i18n/messageCodes.ts and quality:statusRecommendation.codes.* for the
+# human-language mapping in all three supported locales. The backend never emits prose.
+RECOMMENDATION_CODE_ACTIVE_RENTAL = "vehicle.active_rental"
+RECOMMENDATION_CODE_SERVICE_THRESHOLD = "vehicle.service_threshold_reached"
+RECOMMENDATION_CODE_BOOKING_CONFLICT = "vehicle.booking_conflict"
+RECOMMENDATION_CODE_RENTAL_ENDED = "vehicle.rental_ended"
+RECOMMENDATION_CODE_MANUAL_REVIEW = "vehicle.manual_review_required"
+RECOMMENDATION_CODE_NO_CONFLICT = "vehicle.no_conflict"
+
+
+@dataclass
+class VehicleStatusFacts:
+    active_booking_refs: list[str] = field(default_factory=list)
+    overlapping_booking_pairs: list[tuple[str, str]] = field(default_factory=list)
+    service_threshold_reached: bool = False
+    odometer_km: int = 0
+    next_service_km: int = 0
+    open_booking_overlap_issue_ref: str | None = None
+
+    @property
+    def has_active_rental(self) -> bool:
+        return len(self.active_booking_refs) > 0
+
+    @property
+    def has_booking_conflict(self) -> bool:
+        return (
+            len(self.overlapping_booking_pairs) > 0
+            or self.open_booking_overlap_issue_ref is not None
+        )
+
+    def as_dict(self) -> dict:
+        return {
+            "active_booking_refs": self.active_booking_refs,
+            "overlapping_booking_pairs": [list(pair) for pair in self.overlapping_booking_pairs],
+            "service_threshold_reached": self.service_threshold_reached,
+            "odometer_km": self.odometer_km,
+            "next_service_km": self.next_service_km,
+            "open_booking_overlap_issue_ref": self.open_booking_overlap_issue_ref,
+        }
+
+
+@dataclass
+class VehicleStatusRecommendation:
+    current_status: str
+    recommended_status: str | None
+    recommendation_code: str
+    safe_to_apply: bool
+    manual_review_required: bool
+    facts: VehicleStatusFacts
+    blocking_reasons: list[str]
+
+
+def _overlapping_booking_pairs(bookings: list[Booking]) -> list[tuple[Booking, Booking]]:
+    ordered = sorted(bookings, key=lambda b: b.starts_at)
+    pairs: list[tuple[Booking, Booking]] = []
+    for i, first in enumerate(ordered):
+        for second in ordered[i + 1 :]:
+            if second.starts_at < first.ends_at and first.starts_at < second.ends_at:
+                pairs.append((first, second))
+    return pairs
+
+
+def gather_vehicle_status_facts(
+    db: Session, vehicle: Vehicle, *, exclude_issue_id: uuid.UUID | None = None
+) -> VehicleStatusFacts:
+    """Real, freshly-queried facts only -- see module docstring. Never cached, never
+    derived from another issue's mere existence (only a *specific* booking_overlap
+    issue's presence is used, as a cross-reference to that issue's own public_ref)."""
+    reserved_or_active = list(
+        db.scalars(
+            select(Booking).where(
+                Booking.vehicle_id == vehicle.id,
+                Booking.status.in_(["reserved", "active"]),
+            )
+        ).all()
+    )
+    active_refs = [b.public_ref for b in reserved_or_active if b.status == "active"]
+    overlap_pairs = [
+        (a.public_ref, b.public_ref) for a, b in _overlapping_booking_pairs(reserved_or_active)
+    ]
+
+    overlap_issue_query = select(DataQualityIssue.public_ref).where(
+        DataQualityIssue.entity_type == "vehicle",
+        DataQualityIssue.entity_id == vehicle.id,
+        DataQualityIssue.status == "open",
+        DataQualityIssue.rule_type == "booking_overlap",
+    )
+    if exclude_issue_id is not None:
+        overlap_issue_query = overlap_issue_query.where(DataQualityIssue.id != exclude_issue_id)
+    open_overlap_ref = db.scalar(overlap_issue_query)
+
+    return VehicleStatusFacts(
+        active_booking_refs=active_refs,
+        overlapping_booking_pairs=overlap_pairs,
+        service_threshold_reached=vehicle.odometer_km >= vehicle.next_service_km,
+        odometer_km=vehicle.odometer_km,
+        next_service_km=vehicle.next_service_km,
+        open_booking_overlap_issue_ref=open_overlap_ref,
+    )
+
+
+def compute_recommendation_token(vehicle: Vehicle, facts: VehicleStatusFacts) -> str:
+    """A short digest of exactly the facts the recommendation was based on, plus the
+    vehicle's optimistic-lock version. The apply endpoint recomputes this from fresh
+    facts and rejects the request if it doesn't match the token the client last saw --
+    the frontend must never assume a previously-shown preview is still valid without the
+    server re-checking it (see docs/fleet-ops-correction/current-gap-audit.md §8F)."""
+    payload = {"version": vehicle.version, "status": vehicle.operational_status, **facts.as_dict()}
+    digest = hashlib.sha256(json.dumps(payload, sort_keys=True, default=str).encode()).hexdigest()
+    return digest[:16]
+
+
+def evaluate_vehicle_status(
+    vehicle: Vehicle, facts: VehicleStatusFacts
+) -> VehicleStatusRecommendation:
+    """Pure decision logic over already-gathered facts -- see
+    docs/fleet-ops-correction/vehicle-status-decision-table.md. Never mutates anything,
+    never queries the database itself (call gather_vehicle_status_facts first), so it is
+    trivial to unit-test every branch in isolation."""
+    current = vehicle.operational_status
+    blocking_reasons: list[str] = []
+    if facts.service_threshold_reached:
+        blocking_reasons.append(RECOMMENDATION_CODE_SERVICE_THRESHOLD)
+    if facts.has_booking_conflict:
+        blocking_reasons.append(RECOMMENDATION_CODE_BOOKING_CONFLICT)
+    if current == "maintenance" and RECOMMENDATION_CODE_SERVICE_THRESHOLD not in blocking_reasons:
+        # Already being in maintenance is itself a real blocking fact -- an active
+        # booking never overrides it. This is exactly the forbidden shortcut this
+        # evaluator must never take (maintenance + active booking -> auto "rented").
+        blocking_reasons.append(RECOMMENDATION_CODE_SERVICE_THRESHOLD)
+
+    def result(
+        recommended: str | None, code: str, *, safe: bool, manual: bool
+    ) -> VehicleStatusRecommendation:
+        return VehicleStatusRecommendation(
+            current_status=current,
+            recommended_status=recommended,
+            recommendation_code=code,
+            safe_to_apply=safe,
+            manual_review_required=manual,
+            facts=facts,
+            blocking_reasons=blocking_reasons,
+        )
+
+    if facts.has_active_rental and not blocking_reasons:
+        if current == "rented":
+            return result(None, RECOMMENDATION_CODE_NO_CONFLICT, safe=False, manual=False)
+        return result(
+            "rented", RECOMMENDATION_CODE_ACTIVE_RENTAL, safe=True, manual=False
+        )
+
+    if facts.has_active_rental and blocking_reasons:
+        # Explicitly forbidden shortcut this evaluator must never take: an active
+        # booking is not proof the vehicle should be "rented" when a real blocking
+        # condition also exists (e.g. maintenance-due, or a genuine booking conflict).
+        # This is a real contradiction in the underlying facts, not something safe to
+        # resolve automatically.
+        return result(None, RECOMMENDATION_CODE_MANUAL_REVIEW, safe=False, manual=True)
+
+    if facts.service_threshold_reached:
+        if current == "maintenance":
+            return result(None, RECOMMENDATION_CODE_NO_CONFLICT, safe=False, manual=False)
+        return result(
+            "maintenance", RECOMMENDATION_CODE_SERVICE_THRESHOLD, safe=True, manual=False
+        )
+
+    if facts.has_booking_conflict:
+        if current == "blocked":
+            return result(None, RECOMMENDATION_CODE_NO_CONFLICT, safe=False, manual=False)
+        return result(
+            "blocked", RECOMMENDATION_CODE_BOOKING_CONFLICT, safe=True, manual=False
+        )
+
+    # No active rental, no maintenance need, no booking conflict.
+    if current in ("available", "cleaning", "blocked"):
+        return result(None, RECOMMENDATION_CODE_NO_CONFLICT, safe=False, manual=False)
+    if current == "rented":
+        return result(
+            "available", RECOMMENDATION_CODE_RENTAL_ENDED, safe=True, manual=False
+        )
+    if current == "maintenance":
+        # No positive fact confirms maintenance is actually finished (no completed
+        # service record is tracked here) -- clearing "maintenance" without such a
+        # fact would be exactly the kind of unsafe shortcut this evaluator forbids.
+        # Releasing a vehicle from maintenance remains an explicit, manual decision.
+        return result(None, RECOMMENDATION_CODE_NO_CONFLICT, safe=False, manual=False)
+
+    return result(None, RECOMMENDATION_CODE_MANUAL_REVIEW, safe=False, manual=True)