fix(drone): use environment variable for kaniko docker config

.drone.yml

@@ -40,6 +40,9 @@ steps:
 
   - name: docker-build
     image: gcr.io/kaniko-project/executor:latest
+    environment:
+      DOCKER_CONFIG:
+        from_secret: kaniko_secret
     commands:
       - |
         TAG="${DRONE_TAG:-${DRONE_COMMIT_SHA:0:8}}"
@@ -54,9 +57,6 @@ steps:
         /kaniko/executor --context . --dockerfile docker/frontend.Dockerfile --destination ${REGISTRY}/frontend:${TAG} --destination ${REGISTRY}/frontend:latest
         echo "==> All images pushed"
     depends_on: [ frontend-build ]
-    volumes:
-      - name: kaniko-secret
-        path: /kaniko/.dockerconfigjson
 
   - name: prepare-kubeconfig
     image: alpine:latest
@@ -106,11 +106,6 @@ steps:
     when:
       branch: [ main ]
 
-volumes:
-  - name: kaniko-secret
-    secret:
-      secret: kaniko-secret
-
 # =============================================================================
 # Secrets (register via drone CLI)
 # =============================================================================
@@ -124,7 +119,7 @@ volumes:
 #   drone secret add --repository <org/repo> --name kubeconfig --data "$(cat ~/.kube/config | base64 -w 0)"
 #
 # Kaniko dockerconfigjson (for private registry)
-#   drone secret add --repository <org/repo> --name kaniko-secret --data "$(cat ~/.docker/config.json | base64 -w 0)"
+#   drone secret add --repository <org/repo> --name kaniko_secret --data "$(cat ~/.docker/config.json | base64 -w 0)"
 #
 # Local exec:
 #   drone exec --trusted \