fix: unify handler response format in log, permission, webhook handlers

- log_handler.go: Fix GetMyLoginLogs/GetMyOperationLogs/GetLoginLogs/GetOperationLogs to use {code, message, data}
- permission_handler.go: Fix all error responses to use {code, message}
- webhook_handler.go: Add missing "message" field in success responses, wrap data in data object with list/total/page/page_size
- webhook_handler_test.go: Update test to match new response format

Standardize all JSON responses to {code: 0, message: "success", data: ...} for success
and {code: XXX, message: "..."} for errors.

internal/api/handler/webhook_handler_test.go

@@ -255,10 +255,8 @@ func TestWebhookHandler_ListWebhooks_Success(t *testing.T) {
 	if result["code"].(float64) != 0 {
 		t.Fatalf("expected code 0, got %v", result["code"])
 	}
-	if result["data"] == nil {
-		t.Fatal("expected data in response")
-	}
-	if result["total"] == nil {
+	data := result["data"].(map[string]interface{})
+	if data["total"] == nil {
 		t.Fatal("expected total in response")
 	}
 }
@@ -436,15 +434,16 @@ func TestWebhookHandler_ListWebhooks_Pagination(t *testing.T) {
 	var result map[string]interface{}
 	json.NewDecoder(resp.Body).Decode(&result)
 
-	data := result["data"].([]interface{})
-	if len(data) != 2 {
-		t.Fatalf("expected 2 webhooks per page, got %d", len(data))
+	data := result["data"].(map[string]interface{})
+	list := data["list"].([]interface{})
+	if len(list) != 2 {
+		t.Fatalf("expected 2 webhooks per page, got %d", len(list))
 	}
 
-	if result["page"].(float64) != 1 {
-		t.Fatalf("expected page 1, got %v", result["page"])
+	if data["page"].(float64) != 1 {
+		t.Fatalf("expected page 1, got %v", data["page"])
 	}
-	if result["page_size"].(float64) != 2 {
-		t.Fatalf("expected page_size 2, got %v", result["page_size"])
+	if data["page_size"].(float64) != 2 {
+		t.Fatalf("expected page_size 2, got %v", data["page_size"])
 	}
 }