Fix 9 backend bugs: pricing, zones, geocoding, device tokens, assignment retry

- pricingid null: lookupDoormilePrice now returns matched rule ID; wired to BookingServiceOption.Pricingid
- Zone rename: Interstate→Regional, OtherState→National throughout (code + DB migrated)
- Zone from pincodes: CheckPrice now accepts pickup_pincode+delivery_pincode and auto-resolves zone
- Delivery geocoding: pincodeToLatLon() maps 3-digit prefix to city coords when lat/lon are 0
- Device tokens: device_token field added to PinVerify DTOs; saved on both customer and miler login
- Assignment retry: RejectMilerAssignment now re-triggers AssignCustomerMiler/AssignCRMMiler immediately
- Provider empty B2C: defaults to Doormile when no pricing provider row matches
- City gate 422→400: StatusUnprocessableEntity corrected to StatusBadRequest
- Miler GPS 0,0: WS tracking falls back to MilerProfile DB coords when Redis key is expired

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

models/doormile_pricing.go

@@ -2,7 +2,7 @@ package models
 
 import "time"
 
-// Zone values:     Local | Interstate | OtherState
+// Zone values:     Local | Regional | National
 // Category values: General | Documents | Electronics | Clothing | Fragile | Medical | Automotive | Food
 // ServiceType:     Normal | Express