fix: localize dashboard evidence, explain blocked vehicles, clarify pending odometers

Three content defects found by a live reviewer:

- Dashboard attention subtext was raw, untranslated evidence.summary text, and for
  11 of 15 seeded issues that text was literally "Synthetic deterministic seed
  issue". AttentionItem now exposes evidence_signals (stable code + params, same
  shape as the issue detail page) instead of a detail string; the frontend renders
  them through a shared describeEvidenceSignal() used by both the dashboard and the
  issue detail page. Every previously-placeholder seed row now cites a real,
  per-rule-type fact (a genuinely crossed service threshold, a genuinely blank
  field, or a real pair of booking odometer readings) instead of invented prose.

- 5 of 7 blocked vehicles had no quality issue at all and one had only a resolved
  one, so "needs attention" led nowhere. Each now has a real open
  missing_required_field issue backed by a genuinely blank field (no schema change,
  no migration -- reuses the existing data-quality pipeline).

- Booking odometer fields showing a bare "-" for 25 reserved + 1 active booking now
  show a localized explanation ("trip hasn't started yet" / "not yet closed").
  MO-024's rented-but-service-overdue contradiction was already caught by the
  vehicle-status evaluator (DQ-SCAN, vehicle.manual_review_required) -- added a
  regression test rather than new logic.

Also fixed a related bug the above exposed: the vehicle entity_snapshot omitted
registration_number entirely, so the "provide missing fields" form always showed
it blank regardless of the real value.

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

seed/data_quality_issues.csv

@@ -3,14 +3,20 @@ DQ-DEMO-DUPLICATE,possible_duplicate_customer,CUS-0012,CUS-0178,high,open,exact
 DQ-DEMO-OVERLAP,booking_overlap,MO-016,BK-DEMO-OVERLAP-A|BK-DEMO-OVERLAP-B,high,open,controlled legacy import overlap
 DQ-DEMO-STATUS,vehicle_status_conflict,MO-016,,high,open,vehicle marked available while reserved bookings conflict
 DQ-DEMO-ATTENTION,missing_required_field,MO-031,BK-DEMO-NEXT,high,open,near-future booking; required operational inspection missing
-DQ-0005,vehicle_status_conflict,MO-036,,high,open,Synthetic deterministic seed issue
-DQ-0006,missing_required_field,MO-043,,low,open,Synthetic deterministic seed issue
-DQ-0007,odometer_regression,MO-050,,medium,open,Synthetic deterministic seed issue
-DQ-0008,vehicle_status_conflict,MO-007,,high,open,Synthetic deterministic seed issue
-DQ-0009,missing_required_field,MO-014,,low,open,Synthetic deterministic seed issue
-DQ-0010,odometer_regression,MO-021,,medium,open,Synthetic deterministic seed issue
-DQ-0011,vehicle_status_conflict,MO-028,,high,open,Synthetic deterministic seed issue
-DQ-0012,missing_required_field,MO-035,,low,resolved,Synthetic deterministic seed issue
-DQ-0013,odometer_regression,MO-042,,medium,resolved,Synthetic deterministic seed issue
-DQ-0014,vehicle_status_conflict,MO-049,,high,resolved,Synthetic deterministic seed issue
-DQ-0015,missing_required_field,MO-006,,low,resolved,Synthetic deterministic seed issue
+DQ-0005,vehicle_status_conflict,MO-036,,high,open,Recommended status: maintenance (44660 km reported against a 44000 km service threshold)
+DQ-0006,missing_required_field,MO-043,,low,open,Missing: location
+DQ-0007,odometer_regression,MO-050,,medium,open,Booking BK-H-0007 recorded 51700 km, below the 51892 km recorded by earlier booking BK-H-0057.
+DQ-0008,vehicle_status_conflict,MO-007,,high,open,Recommended status: available (marked rented with no active booking)
+DQ-0009,missing_required_field,MO-014,,low,open,Missing: location
+DQ-0010,odometer_regression,MO-021,,medium,open,Booking BK-H-0010 recorded 31150 km, below the 31298 km recorded by earlier booking BK-H-0060.
+DQ-0011,vehicle_status_conflict,MO-028,,high,open,Recommended status: maintenance (38959 km reported against a 38000 km service threshold)
+DQ-0012,missing_required_field,MO-035,,low,resolved,Missing: registration_number
+DQ-0013,missing_required_field,MO-042,,low,resolved,Missing: location
+DQ-0014,missing_required_field,MO-049,,low,resolved,Missing: registration_number
+DQ-0015,missing_required_field,MO-006,,low,resolved,Missing: location
+DQ-0016,missing_required_field,MO-009,,medium,open,Missing: location
+DQ-0017,missing_required_field,MO-025,,medium,open,Missing: location
+DQ-0018,missing_required_field,MO-026,,medium,open,Missing: registration_number
+DQ-0019,missing_required_field,MO-041,,medium,open,Missing: location
+DQ-0020,missing_required_field,MO-045,,medium,open,Missing: location
+DQ-0021,missing_required_field,MO-049,,medium,open,Missing: location