feat: update Protobuf definitions and add customer-facing APIs for various services

src/CMSMicroservice.Protobuf/Protos/userorder.proto

@@ -128,6 +128,12 @@ service UserOrderContract
             body: "*"
         };
     };
+    
+    rpc GetVATRate(google.protobuf.Empty) returns (GetVATRateResponse){
+        option (google.api.http) = {
+            get: "/Customer/GetVATRate"
+        };
+    };
 }
 message CreateNewUserOrderRequest
 {
@@ -526,3 +532,11 @@ message ProductPVDto
     int64 unit_pv = 4;
     int64 total_pv = 5;
 }
+
+// GetVATRate - for frontend customer display
+message GetVATRateResponse
+{
+    double vat_rate = 1;
+    int32 vat_percentage = 2;
+    bool is_enabled = 3;
+}