feat: 支持通过Flyway自动初始化数据库

- 将 starter 初始化脚本迁移到 db/migration，并保留 V1-V3 作为首批迁移

- 清理旧 sql/initdb 挂载与历史分段 SQL，避免 Docker 启动时重复导库

- 更新 README、应用配置和中间件编排，统一空库启动方式

pom.xml

@@ -25,6 +25,7 @@
         <easy-agents.version>0.0.1</easy-agents.version>
         <okhttp.version>4.9.3</okhttp.version>
         <spring-boot.version>3.5.9</spring-boot.version>
+        <flyway.version>10.20.1</flyway.version>
         <slf4j.version>2.0.17</slf4j.version>
         <HikariCP.version>4.0.3</HikariCP.version>
         <fastjson.version>2.0.57</fastjson.version>
@@ -239,6 +240,16 @@
                 <artifactId>spring-boot-starter-actuator</artifactId>
                 <version>${spring-boot.version}</version>
             </dependency>
+            <dependency>
+                <groupId>org.flywaydb</groupId>
+                <artifactId>flyway-core</artifactId>
+                <version>${flyway.version}</version>
+            </dependency>
+            <dependency>
+                <groupId>org.flywaydb</groupId>
+                <artifactId>flyway-mysql</artifactId>
+                <version>${flyway.version}</version>
+            </dependency>
 
             <dependency>
                 <groupId>com.alibaba</groupId>