feat(canvas): Replace emoji icons with professional Lucide React icons

Phase 1 of Canvas Professional Upgrade:
- Replace all emoji icons in nodes with Lucide components
- Update BaseNode to use iconColor prop instead of color/colorBg
- Update NodePalette with matching Lucide icons
- Update templates.ts with Lucide icon names (Box, Scale, BarChart3, etc.)

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

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

@@ -1,13 +1,14 @@
 import { memo } from 'react';
 import { NodeProps } from 'reactflow';
+import { Cpu } from 'lucide-react';
 import { BaseNode } from './BaseNode';
 import { SolverNodeData } from '../../../lib/canvas/schema';
 
 function SolverNodeComponent(props: NodeProps<SolverNodeData>) {
   const { data } = props;
   return (
-    <BaseNode {...props} icon={<span>⚙️</span>} color="text-purple-600" colorBg="bg-purple-50">
-      {data.solverType && <div>{data.solverType}</div>}
+    <BaseNode {...props} icon={<Cpu size={16} />} iconColor="text-violet-400">
+      {data.solverType || 'Select solution'}
     </BaseNode>
   );
 }