Adding error management

src/components/workflows/assets/Workflows.css

@@ -51,12 +51,17 @@
 
 .wkf-canvas {
   position: relative;
+  box-sizing: border-box;
   background-image:
       linear-gradient(rgba(0,0,0,.1) 1px, transparent 1px),
       linear-gradient(90deg, rgba(0,0,0,.1) 1px, transparent 1px);
   background-size: 20px 20px;
 }
 
+.wkf-canvas-error {
+  border: 3px solid var(--color-error);
+}
+
 .wkf-toolbox {
   min-height: 230px;
   width: 8rem;        /* w-32 (32 * 0.25rem = 8rem) */
@@ -89,6 +94,10 @@
     transition: none;
 }
 
+.wkf-workflow-component.error {
+    background: var(--color-error);
+}
+
 .wkf-component-content {
   padding: 0.75rem;           /* p-3 in Tailwind */
   border-radius: 0.5rem;      /* rounded-lg in Tailwind */