feat(mcp): 用 MCP 服务替换内置 AI Agent (#319)

在现有 HTTP 服务挂载 /mcp，让外部 AI 经共享 API Key 调用原分辨率截图、批量键鼠、ATX/WOL 和虚拟介质八个工具。所有调用共用有界 FIFO 和全局限流，复用现有采集管线与硬件控制器。

移除内置模型调用、网页 Agent 面板及旧配置，设置页提供可持续查看的 Key、统一的地址/密钥复制样式。补齐 DEB 的 libudev1 运行依赖。

验证：583 项 Rust 库测试、前端生产构建、ARMv7 设备视觉操作与介质/WOL 实测，以及默认 Release 构建和 DEB 包校验通过。

Refs #319

Cargo.toml

@@ -16,6 +16,7 @@ desktop = [
     "dep:tokio",
     "dep:tokio-util",
     "dep:axum",
+    "dep:rmcp",
     "dep:axum-extra",
     "dep:tower-http",
     "dep:sqlx",
@@ -82,7 +83,9 @@ tokio-util = { version = "0.7", features = ["rt"], optional = true }
 # Web framework
 axum = { version = "0.8", features = ["ws", "multipart", "tokio"], optional = true }
 axum-extra = { version = "0.12", features = ["cookie"], optional = true }
-tower-http = { version = "0.6", features = ["cors", "trace", "set-header"], optional = true }
+tower-http = { version = "0.6", features = ["cors", "trace", "set-header", "limit"], optional = true }
+
+rmcp = { version = "3.5.1", default-features = false, features = ["server", "macros", "schemars", "transport-streamable-http-server"], optional = true }
 
 # Database - Use bundled SQLite for static linking
 sqlx = { version = "0.9", default-features = false, features = ["runtime-tokio", "sqlite-bundled"], optional = true }