feat: add Go MCP server list API (#15253)

## What
#15240 
Implements `GET /api/v1/mcp/servers` in the Go API server.

## Changes

- Added MCP server DAO list query with tenant scoping.
- Added MCP service response wrapper.
- Added MCP handler for list request parsing and response formatting.
- Wired `GET /api/v1/mcp/servers` under authenticated `/api/v1` routes.
- Initialized MCP service and handler in the Go server startup.
- update_time and update_date now both map to update_date
- create_time and create_date now both map to create_date
- default ordering now returns create_date
## API Behavior

Matches the Python endpoint behavior:

- Requires authenticated user.
- Lists MCP servers for the current user tenant.
- Supports `keywords`.
- Supports `mcp_id` and repeated/comma-separated `mcp_ids`.
- Supports `page`, `page_size`, `orderby`, and `desc`.
- Returns:

```json
{
  "code": 0,
  "message": "success",
  "data": {
    "mcp_servers": [],
    "total": 0
  }
}
```

internal/handler/mcp.go

@@ -17,7 +17,10 @@
 package handler
 
 import (
+	"fmt"
 	"net/http"
+	"strconv"
+	"strings"
 
 	"github.com/gin-gonic/gin"
 
@@ -25,6 +28,12 @@ import (
 	"ragflow/internal/service"
 )
 
+const (
+	defaultMCPServerPage     = 0
+	defaultMCPServerPageSize = 0
+	maxMCPServerPageSize     = 100
+)
+
 // MCPHandler handles MCP server requests.
 type MCPHandler struct {
 	mcpService *service.MCPService
@@ -64,6 +73,51 @@ func (h *MCPHandler) CreateMCPServer(c *gin.Context) {
 	})
 }
 
+// ListMCPServers lists MCP servers for the current user.
+func (h *MCPHandler) ListMCPServers(c *gin.Context) {
+	user, errorCode, errorMessage := GetUser(c)
+	if errorCode != common.CodeSuccess {
+		jsonError(c, errorCode, errorMessage)
+		return
+	}
+
+	page, err := parseMCPServerPage(c.Query("page"))
+	if err != nil {
+		jsonError(c, common.CodeDataError, err.Error())
+		return
+	}
+	pageSize, err := parseMCPServerPageSize(c.Query("page_size"))
+	if err != nil {
+		jsonError(c, common.CodeDataError, err.Error())
+		return
+	}
+
+	orderby := c.DefaultQuery("orderby", "create_time")
+	desc := strings.ToLower(c.DefaultQuery("desc", "true")) != "false"
+	keywords := c.Query("keywords")
+	mcpIDs := getMCPIDsFromQuery(c)
+
+	result, code, err := h.mcpService.ListMCPServers(user.ID, mcpIDs, keywords, page, pageSize, orderby, desc)
+	if err != nil {
+		if code == common.CodeServerError {
+			c.JSON(http.StatusInternalServerError, gin.H{
+				"code":    code,
+				"message": err.Error(),
+				"data":    nil,
+			})
+			return
+		}
+		jsonError(c, code, err.Error())
+		return
+	}
+
+	c.JSON(http.StatusOK, gin.H{
+		"code":    common.CodeSuccess,
+		"message": "success",
+		"data":    result,
+	})
+}
+
 // DeleteMCPServer deletes an MCP server for the current user.
 func (h *MCPHandler) DeleteMCPServer(c *gin.Context) {
 	user, errorCode, errorMessage := GetUser(c)
@@ -84,3 +138,46 @@ func (h *MCPHandler) DeleteMCPServer(c *gin.Context) {
 		"data":    result,
 	})
 }
+
+func parseMCPServerPage(value string) (int, error) {
+	if value == "" {
+		return defaultMCPServerPage, nil
+	}
+	page, err := strconv.Atoi(value)
+	if err != nil {
+		return 0, fmt.Errorf("page must be an integer")
+	}
+	return page, nil
+}
+
+func parseMCPServerPageSize(value string) (int, error) {
+	if value == "" {
+		return defaultMCPServerPageSize, nil
+	}
+	pageSize, err := strconv.Atoi(value)
+	if err != nil {
+		return 0, fmt.Errorf("page_size must be an integer")
+	}
+	if pageSize > maxMCPServerPageSize {
+		return 0, fmt.Errorf("page_size must be less than or equal to %d", maxMCPServerPageSize)
+	}
+	return pageSize, nil
+}
+
+func getMCPIDsFromQuery(c *gin.Context) []string {
+	rawValues := c.QueryArray("mcp_ids")
+	if len(rawValues) == 0 {
+		rawValues = []string{c.Query("mcp_id")}
+	}
+
+	ids := make([]string, 0)
+	for _, rawValue := range rawValues {
+		for _, item := range strings.Split(rawValue, ",") {
+			id := strings.TrimSpace(item)
+			if id != "" {
+				ids = append(ids, id)
+			}
+		}
+	}
+	return ids
+}