refactor: 重构项目结构，迁移后端至 mengyastore-backend-go，新增 Java 后端、前端功能更新及部署文档

mengyastore-backend-go/mengyastore-backend-java/src/main/java/com/smyhub/store/mengyastorebackendjava/MengyastoreBackendJavaApplication.java

@@ -0,0 +1,13 @@
+package com.smyhub.store.mengyastorebackendjava;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class MengyastoreBackendJavaApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(MengyastoreBackendJavaApplication.class, args);
+    }
+
+}

mengyastore-backend-go/mengyastore-backend-java/src/main/resources/application.yaml

@@ -0,0 +1,3 @@
+spring:
+  application:
+    name: mengyastore-backend-java

mengyastore-backend-go/mengyastore-backend-java/src/test/java/com/smyhub/store/mengyastorebackendjava/MengyastoreBackendJavaApplicationTests.java

@@ -0,0 +1,13 @@
+package com.smyhub.store.mengyastorebackendjava;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.test.context.SpringBootTest;
+
+@SpringBootTest
+class MengyastoreBackendJavaApplicationTests {
+
+    @Test
+    void contextLoads() {
+    }
+
+}