新增系统配置表及默认配置，更新链接生成请求DTO以支持链接数量参数，重构链接生成服务逻辑，添加链接状态查询和有效性检查接口，优化日志记录。

target/classes/mapper/admin/SystemConfigMapper.xml

@@ -0,0 +1,68 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
+<mapper namespace="com.gameplatform.server.mapper.admin.SystemConfigMapper">
+    <resultMap id="SystemConfigMap" type="com.gameplatform.server.model.entity.admin.SystemConfig">
+        <id property="id" column="id" />
+        <result property="configKey" column="config_key" />
+        <result property="configValue" column="config_value" />
+        <result property="configType" column="config_type" />
+        <result property="description" column="description" />
+        <result property="isSystem" column="is_system" />
+        <result property="createdAt" column="created_at" />
+        <result property="updatedAt" column="updated_at" />
+    </resultMap>
+
+    <select id="findById" parameterType="long" resultMap="SystemConfigMap">
+        SELECT id, config_key, config_value, config_type, description, is_system, created_at, updated_at
+        FROM system_config
+        WHERE id = #{id}
+        LIMIT 1
+    </select>
+
+    <select id="findByKey" parameterType="string" resultMap="SystemConfigMap">
+        SELECT id, config_key, config_value, config_type, description, is_system, created_at, updated_at
+        FROM system_config
+        WHERE config_key = #{configKey}
+        LIMIT 1
+    </select>
+
+    <select id="findByType" parameterType="string" resultMap="SystemConfigMap">
+        SELECT id, config_key, config_value, config_type, description, is_system, created_at, updated_at
+        FROM system_config
+        WHERE config_type = #{configType}
+        ORDER BY config_key ASC
+    </select>
+
+    <select id="findAll" resultMap="SystemConfigMap">
+        SELECT id, config_key, config_value, config_type, description, is_system, created_at, updated_at
+        FROM system_config
+        ORDER BY config_key ASC
+        LIMIT #{size} OFFSET #{offset}
+    </select>
+
+    <select id="countAll" resultType="long">
+        SELECT COUNT(1) FROM system_config
+    </select>
+
+    <insert id="insert" parameterType="com.gameplatform.server.model.entity.admin.SystemConfig" useGeneratedKeys="true" keyProperty="id">
+        INSERT INTO system_config (config_key, config_value, config_type, description, is_system)
+        VALUES (#{configKey}, #{configValue}, #{configType}, #{description}, #{isSystem})
+    </insert>
+
+    <update id="update" parameterType="com.gameplatform.server.model.entity.admin.SystemConfig">
+        UPDATE system_config
+        SET config_value = #{configValue},
+            config_type = #{configType},
+            description = #{description},
+            is_system = #{isSystem}
+        WHERE id = #{id}
+    </update>
+
+    <delete id="deleteById" parameterType="long">
+        DELETE FROM system_config WHERE id = #{id}
+    </delete>
+
+    <delete id="deleteByKey" parameterType="string">
+        DELETE FROM system_config WHERE config_key = #{configKey}
+    </delete>
+</mapper>