feat: Phase 1 - Canvas with React Flow

- 8 node types (Model, Solver, DesignVar, Extractor, Objective, Constraint, Algorithm, Surrogate)
- Drag-drop from palette to canvas
- Node configuration panels
- Graph validation with error/warning display
- Intent JSON serialization
- Zustand state management

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

atomizer-dashboard/frontend/src/components/canvas/nodes/ExtractorNode.tsx

@@ -0,0 +1,17 @@
+import { memo } from 'react';
+import { NodeProps } from 'reactflow';
+import { BaseNode } from './BaseNode';
+import { ExtractorNodeData } from '../../../lib/canvas/schema';
+
+function ExtractorNodeComponent(props: NodeProps<ExtractorNodeData>) {
+  const { data } = props;
+  return (
+    <BaseNode {...props} icon={<span>🔬</span>} color="text-cyan-600">
+      {data.extractorName && <div>{data.extractorName}</div>}
+      {data.extractorId && (
+        <div className="text-xs text-gray-400">{data.extractorId}</div>
+      )}
+    </BaseNode>
+  );
+}
+export const ExtractorNode = memo(ExtractorNodeComponent);