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

src/web/handlers/mcp.rs

@@ -0,0 +1,82 @@
+use crate::{
+    error::{AppError, Result},
+    state::AppState,
+};
+use axum::{extract::State, http::header, Json};
+use serde::{Deserialize, Serialize};
+use std::sync::Arc;
+
+#[derive(Serialize)]
+pub struct McpConfigResponse {
+    pub enabled: bool,
+    pub requests_per_second: u32,
+    pub api_key_configured: bool,
+    pub endpoint: &'static str,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub api_key: Option<String>,
+}
+#[derive(Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct McpConfigUpdate {
+    pub enabled: Option<bool>,
+    pub requests_per_second: Option<u32>,
+    #[serde(default)]
+    pub regenerate_api_key: bool,
+}
+fn response(state: &AppState) -> McpConfigResponse {
+    let config = state.config.get();
+    McpConfigResponse {
+        enabled: config.mcp.enabled,
+        requests_per_second: config.mcp.requests_per_second,
+        api_key_configured: config.mcp.api_key_hash.is_some(),
+        endpoint: "/mcp",
+        api_key: config.mcp.api_key.clone(),
+    }
+}
+pub async fn mcp_config(
+    State(state): State<Arc<AppState>>,
+) -> (
+    [(header::HeaderName, &'static str); 1],
+    Json<McpConfigResponse>,
+) {
+    (
+        [(header::CACHE_CONTROL, "no-store")],
+        Json(response(&state)),
+    )
+}
+pub async fn mcp_update_config(
+    State(state): State<Arc<AppState>>,
+    Json(req): Json<McpConfigUpdate>,
+) -> Result<(
+    [(header::HeaderName, &'static str); 1],
+    Json<McpConfigResponse>,
+)> {
+    if req
+        .requests_per_second
+        .is_some_and(|rate| !(1..=100).contains(&rate))
+    {
+        return Err(AppError::BadRequest(
+            "requests_per_second must be between 1 and 100".into(),
+        ));
+    }
+    state
+        .config
+        .update(|config| {
+            if let Some(enabled) = req.enabled {
+                config.mcp.enabled = enabled;
+            }
+            if let Some(rate) = req.requests_per_second {
+                config.mcp.requests_per_second = rate;
+            }
+            if req.regenerate_api_key || (config.mcp.enabled && config.mcp.api_key_hash.is_none()) {
+                let key = crate::mcp::generate_key();
+                config.mcp.api_key_hash = Some(crate::mcp::hash_key(&key));
+                config.mcp.api_key = Some(key);
+            }
+        })
+        .await?;
+    Ok((
+        [(header::CACHE_CONTROL, "no-store")],
+        Json(response(&state)),
+    ))
+}