feat: admin notification system with priority ordering, bell icon, and /notifications page

Two-tier notification system: new_booking (all public bookings) + pending_booking (notes/today).
Priority-sorted queue, unread count polling, enriched responses with user_name/booking_start_time.
Fix critical bug: edit_requested cleanup was broken (wrong reason string in 3 handlers).
Add 15 new tests covering priority ordering, enrichment, and notification creation flows.
Update Admin Manual, Technical Manual, and gap backlog docs.

backend/auth/jwt.go

@@ -36,17 +36,20 @@ func VerifyToken(tokenString string, ctx context.Context) (userID string, role s
 		return "", "", err
 	}
 
-	claims, err := token.AsMap(ctx)
-	if err != nil {
-		return "", "", err
+	var uidVal interface{}
+	if err := token.Get("user_id", &uidVal); err != nil {
+		return "", "", fmt.Errorf("invalid user_id claim")
 	}
-
-	userID, ok := claims["user_id"].(string)
+	userID, ok := uidVal.(string)
 	if !ok {
 		return "", "", fmt.Errorf("invalid user_id claim")
 	}
 
-	role, ok = claims["role"].(string)
+	var roleVal interface{}
+	if err := token.Get("role", &roleVal); err != nil {
+		return "", "", fmt.Errorf("invalid role claim")
+	}
+	role, ok = roleVal.(string)
 	if !ok {
 		return "", "", fmt.Errorf("invalid role claim")
 	}