Add wallet balance to User model and implement Atoll/Island management

- Added `wallet_balance` field to the User model.
- Updated UserAdmin to include `wallet_balance` in the admin interface.
- Created serializers and views for Atoll and Island management.
- Implemented endpoints for listing, creating, and updating Atolls and Islands.
- Enhanced payment processing with UUIDs for Payment and Topup models.
- Added migration files for new fields and constraints.
- Improved error handling and validation in various views.
- Updated email templates for better responsiveness and SEO.

api/admin.py

@@ -15,6 +15,7 @@ class UserAdmin(BaseUserAdmin):
         "is_staff",
         "mobile",
         "address",
+        "wallet_balance",
         "acc_no",
         "id_card",
         "dob",
@@ -35,6 +36,7 @@ class UserAdmin(BaseUserAdmin):
                     "email",
                     "mobile",
                     "address",
+                    "wallet_balance",
                     "acc_no",
                     "id_card",
                     "dob",