feat(keyboard): 新增键盘用户管理模块

新增 keyboard-server 子模块，含用户 DO/Mapper/Service/Controller 全套代码；
补充错误码 KEYBOARD_USER_NOT_EXISTS；
主工程引入 keyboard-server 依赖并扩展包扫描路径。

keyboard-server/pom.xml

@@ -0,0 +1,56 @@
+<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>com.yolo</groupId>
+        <artifactId>yolo</artifactId>
+        <version>${revision}</version>
+    </parent>
+    <packaging>jar</packaging> <!-- 2. 新增 packaging 为 jar -->
+    <artifactId>keyboard-server</artifactId>
+
+    <name>${project.artifactId}</name>
+    <url>http://maven.apache.org</url>
+    <description> <!-- 4. 新增 description 为该模块的描述 -->
+        键盘后台服务
+    </description>
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+    <dependencies>
+        <!-- Web 相关 -->
+        <dependency>
+            <groupId>com.yolo</groupId>
+            <artifactId>yolo-spring-boot-starter-web</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.yolo</groupId>
+            <artifactId>yolo-spring-boot-starter-security</artifactId>
+        </dependency>
+
+        <!-- DB 相关 -->
+        <dependency>
+            <groupId>com.yolo</groupId>
+            <artifactId>yolo-spring-boot-starter-mybatis</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>3.8.1</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.yolo</groupId>
+            <artifactId>yolo-spring-boot-starter-excel</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.yolo</groupId>
+            <artifactId>yolo-module-infra</artifactId>
+            <version>2025.11-SNAPSHOT</version>
+            <scope>compile</scope>
+        </dependency>
+    </dependencies>
+</project>