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>

middlewares/city_gate.go

@@ -33,7 +33,7 @@ func CityGateMiddleware(c *fiber.Ctx) error {
 		}
 	}
 
-	return c.Status(fiber.StatusUnprocessableEntity).JSON(fiber.Map{
+	return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{
 		"error": "We are not yet operating in your city. Stay tuned!",
 		"code":  "CITY_NOT_SUPPORTED",
 	})