feat: 搭建后端多租户名片服务

- 初始化 Spring Boot 多模块工程与通用基础能力

- 增加租户、组织、用户、名片、文件、统计等业务模块

- 补充数据库迁移脚本与基础测试

backend/easycard-module-system/pom.xml

@@ -0,0 +1,22 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <parent>
+    <groupId>com.easycard</groupId>
+    <artifactId>easycard-parent</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+  </parent>
+
+  <artifactId>easycard-module-system</artifactId>
+  <name>easycard-module-system</name>
+
+  <dependencies>
+    <dependency>
+      <groupId>com.easycard</groupId>
+      <artifactId>easycard-common</artifactId>
+      <version>${project.version}</version>
+    </dependency>
+  </dependencies>
+</project>