fix: Remove unused imports and variables in catalog.go

- Removed unused encoding/json and io/ioutil imports
- Commented out unused tag variable

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: anubissbe

backend/mcp/catalog.go

@@ -1,9 +1,7 @@
 package mcp
 
 import (
-	"encoding/json"
 	"fmt"
-	"io/ioutil"
 	"net/http"
 	"strings"
 	"time"
@@ -259,7 +257,7 @@ func GetPredefinedConfig(fullName string) (*MCPConfig, error) {
 	}
 
 	imageName := parts[0]
-	tag := parts[1]
+	// tag := parts[1] // Reserved for future use
 
 	// Return predefined configs for known servers
 	switch imageName {