Add assignment engine, FCM, WebSockets, city gate, and internal APIs

- internal/assignment: GEORADIUS miler assignment with retry/escalation,
  customer-side provider scoring, FCM notifications on assign
- internal/notify: Firebase Admin SDK (FCM) client initialisation
- internal/ws: WebSocket handlers for live parcel tracking and
  customer↔miler chat
- middlewares: city gate (pincode prefix validation), internal API key
  auth, WebSocket JWT auth
- controllers: InternalNotify + InternalReassign for machine-to-machine
  calls; pricing helpers wired into CreateCustomerBooking and CreateCRMBooking
- routes: /internal/*, /ws/bookings/:id/track, /ws/bookings/:id/chat
- models/users, models/doormile_pricing: new fields for device tokens,
  assignment state, pricing bands
- seed_data.sql: initial pricing seed rows

.env and Firebase service-account JSON intentionally excluded.

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

controllers/pricing_helpers.go

@@ -0,0 +1,119 @@
+package controllers
+
+import (
+	"context"
+	"encoding/json"
+	"strconv"
+	"time"
+
+	"doormile/db"
+	"doormile/models"
+	"doormile/utils"
+)
+
+// pincodeToState maps an Indian pincode to a state key using its first 3 digits.
+// Covers the states Doormile operates in; other pincodes fall back to their 2-digit prefix.
+func pincodeToState(pincode string) string {
+	if len(pincode) < 3 {
+		return pincode
+	}
+	p, err := strconv.Atoi(pincode[:3])
+	if err != nil {
+		if len(pincode) >= 2 {
+			return pincode[:2]
+		}
+		return pincode
+	}
+	switch {
+	case p >= 500 && p <= 535:
+		return "AP_TS" // Andhra Pradesh / Telangana
+	case p >= 560 && p <= 591:
+		return "KA" // Karnataka
+	case p >= 600 && p <= 643:
+		return "TN" // Tamil Nadu
+	case p >= 670 && p <= 695:
+		return "KL" // Kerala
+	case p >= 380 && p <= 396:
+		return "GJ" // Gujarat
+	case p >= 400 && p <= 444:
+		return "MH" // Maharashtra
+	default:
+		if len(pincode) >= 2 {
+			return pincode[:2]
+		}
+		return pincode
+	}
+}
+
+// resolveZone determines the DoormilePricing zone from pickup and delivery pincodes.
+//   - Local     — same 3-digit prefix (same city/sorting district)
+//   - Interstate — different city, same state
+//   - OtherState — different state
+func resolveZone(pickupPincode, deliveryPincode string) string {
+	if len(pickupPincode) >= 3 && len(deliveryPincode) >= 3 && pickupPincode[:3] == deliveryPincode[:3] {
+		return "Local"
+	}
+	if pincodeToState(pickupPincode) == pincodeToState(deliveryPincode) {
+		return "Interstate"
+	}
+	return "OtherState"
+}
+
+// normalizePricingCategory returns a DoormilePricing-compatible category string.
+// Falls back to "General" for unknown or empty values.
+func normalizePricingCategory(category string) string {
+	switch category {
+	case "General", "Documents", "Electronics", "Clothing", "Fragile", "Medical", "Automotive", "Food":
+		return category
+	default:
+		return "General"
+	}
+}
+
+// mapServiceTypeToPricing maps the booking service type to a DoormilePricing service type.
+// DoormilePricing has only Normal and Express.
+func mapServiceTypeToPricing(serviceType string) string {
+	if serviceType == "Fast" || serviceType == "Superfast" {
+		return "Express"
+	}
+	return "Normal"
+}
+
+// lookupDoormilePrice fetches pricing for the given zone/serviceType/weight/category
+// from Redis first, falling back to Postgres on a cache miss.
+// Returns the midpoint of the matched price band and true, or 0 and false if no rule matches.
+func lookupDoormilePrice(zone, pricingServiceType string, weight float64, category string) (float64, bool) {
+	var allRules []models.DoormilePricing
+
+	if db.Rdb != nil {
+		ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+		cached, err := db.Rdb.Get(ctx, pricingCacheKey(zone, pricingServiceType)).Result()
+		cancel()
+		if err == nil {
+			if jerr := json.Unmarshal([]byte(cached), &allRules); jerr != nil {
+				utils.Warn("Corrupt pricing cache in booking, evicting", "zone", zone, "servicetype", pricingServiceType)
+				invalidatePricingCache(zone, pricingServiceType)
+				allRules = nil
+			}
+		}
+	}
+
+	if allRules == nil {
+		var err error
+		allRules, err = loadFromPostgres(zone, pricingServiceType)
+		if err != nil || len(allRules) == 0 {
+			return 0, false
+		}
+	}
+
+	matched := applyFilters(allRules, weight, category)
+	if len(matched) == 0 && category != "General" {
+		matched = applyFilters(allRules, weight, "General")
+	}
+	if len(matched) == 0 {
+		return 0, false
+	}
+
+	rule := matched[0]
+	return (rule.Minprice + rule.Maxprice) / 2, true
+}