feat(dev-server): 添加开发模式 HTTP/WebSocket 服务器

功能:
- 创建 dev_server.rs 模块，提供 HTTP/WebSocket API
- 使用 feature flag \dev-server\ 控制编译
- 仅绑定 localhost:50051，安全限制 CORS
- 生产构建不包含此模块

使用方式:
- pnpm tauri:dev:web - 启动带开发服务器的 Tauri
- pnpm tauri:dev - 常规开发模式（无服务器）

安全:
- 仅 localhost 绑定
- CORS 限制为 Vite 开发端口
- 通过 feature flag 完全移除生产代码

desktop/src-tauri/Cargo.toml

@@ -15,6 +15,10 @@ crate-type = ["staticlib", "cdylib", "rlib"]
 [build-dependencies]
 tauri-build = { version = "2", features = [] }
 
+[features]
+default = []
+dev-server = ["axum", "tower-http"]
+
 [dependencies]
 # ZCLAW crates
 zclaw-types = { workspace = true }
@@ -66,3 +70,7 @@ rand = { workspace = true }
 
 # SQLite (keep for backward compatibility during migration)
 sqlx = { workspace = true }
+
+# Development server (optional, only for debug builds)
+axum = { version = "0.7", features = ["ws"], optional = true }
+tower-http = { version = "0.5", optional = true }