[fix](server): update domain status response types for consistency

- Changed `CreatedAt` and `UpdatedAt` fields in `domainStatusResponse` to `time.Time` for type consistency and improved parsing.

internal/admin/http.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"net/http"
 	"strings"
+	"time"
 
 	"github.com/dalbodeule/hop-gate/internal/logging"
 )
@@ -145,8 +146,8 @@ type domainStatusResponse struct {
 	Exists    bool      `json:"exists"`
 	Domain    string    `json:"domain,omitempty"`
 	Memo      string    `json:"memo,omitempty"`
-	CreatedAt any    `json:"created_at,omitempty"`
-	UpdatedAt any    `json:"updated_at,omitempty"`
+	CreatedAt time.Time `json:"created_at,omitempty"`
+	UpdatedAt time.Time `json:"updated_at,omitempty"`
 	Error     string    `json:"error,omitempty"`
 }