feat(server): 添加游戏服务器框架 | add game server framework (#366)

**@esengine/server** - 游戏服务器框架 | Game server framework
- 文件路由系统 | File-based routing
- Room 生命周期 (onCreate, onJoin, onLeave, onTick, onDispose)
- @onMessage 装饰器 | Message handler decorator
- 玩家管理与断线处理 | Player management with auto-disconnect
- 内置 JoinRoom/LeaveRoom API | Built-in room APIs
- defineApi/defineMsg 类型安全辅助函数 | Type-safe helpers

**create-esengine-server** - CLI 脚手架工具 | CLI scaffolding
- 生成 shared/server/client 项目结构 | Project structure
- 类型安全的协议定义 | Type-safe protocol definitions
- 包含 GameRoom 示例 | Example implementation

**其他 | Other**
- 删除旧的 network-server 包 | Remove old network-server
- 更新服务器文档 | Update server documentation

packages/framework/server/src/helpers/define.ts

@@ -0,0 +1,51 @@
+/**
+ * @zh API 和消息定义助手
+ * @en API and message definition helpers
+ */
+
+import type { ApiDefinition, MsgDefinition } from '../types/index.js'
+
+/**
+ * @zh 定义 API 处理器
+ * @en Define API handler
+ *
+ * @example
+ * ```typescript
+ * // src/api/join.ts
+ * import { defineApi } from '@esengine/server'
+ *
+ * export default defineApi<ReqJoin, ResJoin>({
+ *     handler(req, ctx) {
+ *         ctx.conn.data.playerId = generateId()
+ *         return { playerId: ctx.conn.data.playerId }
+ *     }
+ * })
+ * ```
+ */
+export function defineApi<TReq, TRes, TData = Record<string, unknown>>(
+    definition: ApiDefinition<TReq, TRes, TData>
+): ApiDefinition<TReq, TRes, TData> {
+    return definition
+}
+
+/**
+ * @zh 定义消息处理器
+ * @en Define message handler
+ *
+ * @example
+ * ```typescript
+ * // src/msg/input.ts
+ * import { defineMsg } from '@esengine/server'
+ *
+ * export default defineMsg<MsgInput>({
+ *     handler(msg, ctx) {
+ *         console.log('Input from', ctx.conn.id, msg)
+ *     }
+ * })
+ * ```
+ */
+export function defineMsg<TMsg, TData = Record<string, unknown>>(
+    definition: MsgDefinition<TMsg, TData>
+): MsgDefinition<TMsg, TData> {
+    return definition
+}