feat(mcp): 设置 → MCP 子页 + 策略 API + 官网/文档接入

借鉴 DBX：安装检测（Node/npm/包/Go 二进制）、只读与 allow_dangerous、
连接白名单、多客户端配置片段；GET/PUT /api/ai/mcp-policy、/mcp-install；
文档 /docs/mcp 与落地页 AI/MCP 块；对照 docs/16 勾选设置项、列仍未完清单。

server/internal/server/router.go

@@ -584,6 +584,49 @@ func NewRouter(token string) *gin.Engine {
 			c.JSON(http.StatusOK, aitools.GetMCPStatus())
 		})
 
+		// MCP 策略读写（设置 → MCP）：~/.opsxdb/mcp.json
+		api.GET("/ai/mcp-policy", func(c *gin.Context) {
+			p, err := aitools.LoadPolicy()
+			if err != nil {
+				c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+				return
+			}
+			path, _ := aitools.PolicyPath()
+			c.JSON(http.StatusOK, gin.H{"policy": p, "path": path})
+		})
+
+		api.PUT("/ai/mcp-policy", func(c *gin.Context) {
+			var req struct {
+				AllowedConnectionIDs []string `json:"allowed_connection_ids"`
+				Mode                 string   `json:"mode"`
+				AllowDangerous       bool     `json:"allow_dangerous"`
+				DefaultLimit         int      `json:"default_limit"`
+				MaxLimit             int      `json:"max_limit"`
+			}
+			if err := c.ShouldBindJSON(&req); err != nil {
+				c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+				return
+			}
+			p := aitools.Policy{
+				AllowedConnectionIDs: req.AllowedConnectionIDs,
+				Mode:                 req.Mode,
+				AllowDangerous:       req.AllowDangerous,
+				DefaultLimit:         req.DefaultLimit,
+				MaxLimit:             req.MaxLimit,
+			}
+			if err := aitools.SavePolicy(p); err != nil {
+				c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+				return
+			}
+			saved, _ := aitools.LoadPolicy()
+			path, _ := aitools.PolicyPath()
+			c.JSON(http.StatusOK, gin.H{"ok": true, "policy": saved, "path": path})
+		})
+
+		api.GET("/ai/mcp-install", func(c *gin.Context) {
+			c.JSON(http.StatusOK, aitools.ProbeMCPInstall())
+		})
+
 		api.POST("/ai/generate", func(c *gin.Context) {
 			var req ai.ChatReq
 			if err := c.ShouldBindJSON(&req); err != nil {