feat: miler delivery-leg fixes — consignmentid, auto route sequencing, admin consignment status

Miler app P0 + contract gaps found in the live audit:

- GET /miler/bookings now returns consignmentid + consignmentstatus on every
  row (nullable), so the app can call deliver/skip/start-delivery straight from
  the list. /miler/assignments is the active-only queue, so this is the
  authoritative fix for stops that have moved onto the delivery leg.
- GET /miler/bookings now returns sequencedat per row: non-null means the
  console/optimizer fixed this stop's order and the app follows step exactly;
  null means no route assigned and the app may fall back to nearest-first.
- Route sequencing (internal/routing) now runs automatically after every
  assignment — customer auto-assign, express auto-assign, manual assign, and
  accept — via SequenceMilerStopsAsync (fire-and-forget, no-op below two active
  stops). Previously only hub batch-assign sequenced, so most riders saw step=0.
- GET /admin/bookings now surfaces the live consignmentstatus alongside the
  frozen booking status, so a Converted_To_Consignment booking can still show
  Out_for_Delivery / Delivered instead of a generic "Active".

Two-step hyperlocal flow (Arrived_At_Pickup, Collected_By_Miler, start-delivery)
stays gated behind MILER_COLLECTED_STATE_ENABLED (default off) until the app
ships; consignmentid/status, GET /miler/consignments/:id, stable error codes and
Idempotency-Key handling are unconditional and safe on the current app.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WRaFH5hMRqmUQvVPQsyjZD

models/booking.go

@@ -44,8 +44,14 @@ type PickupBooking struct {
 	Preferredpickupto   *time.Time `json:"preferredpickupto" gorm:"column:preferredpickupto"`
 	Assignedmileruserid *int       `json:"assignedmileruserid" gorm:"column:assignedmileruserid"`
 	Consignmentid       *int       `json:"consignmentid" gorm:"column:consignmentid"`
-	Createdat           time.Time  `json:"createdat" gorm:"column:createdat;default:CURRENT_TIMESTAMP"`
-	Updatedat           time.Time  `json:"updatedat" gorm:"column:updatedat;default:CURRENT_TIMESTAMP"`
+	// Consignmentstatus is not a column — it is filled in by handlers that want
+	// the live consignment status alongside the booking (e.g. the admin bookings
+	// list, so a "Converted_To_Consignment" booking can still show
+	// Out_for_Delivery / Delivered). omitempty keeps it out of every other
+	// PickupBooking response that does not populate it.
+	Consignmentstatus string    `json:"consignmentstatus,omitempty" gorm:"-"`
+	Createdat         time.Time `json:"createdat" gorm:"column:createdat;default:CURRENT_TIMESTAMP"`
+	Updatedat         time.Time `json:"updatedat" gorm:"column:updatedat;default:CURRENT_TIMESTAMP"`
 
 	// Relations
 	Parcels        []BookingParcel        `json:"parcels" gorm:"foreignKey:Bookingid"`