feat: UI/UX redesign for MCP Apps - 3 new apps + enhanced existing (#583)

Add workflow-list, execution-history, and health-dashboard apps.
Redesign operation-result with operation-aware headers, detail panels,
and copy-to-clipboard. Fix React hooks violations in validation-summary
and execution-history (useMemo after early returns). Add local preview
harness for development. Update tests for 5-app config.

Conceived by Romuald Członkowski - www.aiadvisors.pl/en

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

ui-apps/src/shared/components/CopyButton.tsx

@@ -0,0 +1,54 @@
+import React, { useState, useCallback } from 'react';
+
+interface CopyButtonProps {
+  text: string;
+}
+
+export function CopyButton({ text }: CopyButtonProps) {
+  const [copied, setCopied] = useState(false);
+
+  const handleCopy = useCallback(async () => {
+    try {
+      await navigator.clipboard.writeText(text);
+      setCopied(true);
+      setTimeout(() => setCopied(false), 2000);
+    } catch {
+      // Fallback for sandboxed environments
+      const ta = document.createElement('textarea');
+      ta.value = text;
+      ta.style.position = 'fixed';
+      ta.style.opacity = '0';
+      document.body.appendChild(ta);
+      ta.select();
+      document.execCommand('copy');
+      document.body.removeChild(ta);
+      setCopied(true);
+      setTimeout(() => setCopied(false), 2000);
+    }
+  }, [text]);
+
+  return (
+    <button
+      onClick={handleCopy}
+      style={{
+        display: 'inline-flex',
+        alignItems: 'center',
+        justifyContent: 'center',
+        width: '20px',
+        height: '20px',
+        padding: 0,
+        border: '1px solid var(--n8n-border)',
+        borderRadius: '4px',
+        background: 'transparent',
+        color: copied ? 'var(--n8n-success)' : 'var(--n8n-text-muted)',
+        cursor: 'pointer',
+        fontSize: '11px',
+        lineHeight: 1,
+        flexShrink: 0,
+      }}
+      title="Copy"
+    >
+      {copied ? '✓' : '⎘'}
+    </button>
+  );
+}