feat: Add Canvas dark theme styling and Setup page integration

Canvas Builder Visual Updates:
- Update all Canvas components to use Atomaster dark theme
- BaseNode: dark background (bg-dark-800), white text, primary selection glow
- NodePalette: dark sidebar with hover states
- NodeConfigPanel: dark inputs, labels, and panel background
- ValidationPanel: semi-transparent error/warning panels with backdrop blur
- ChatPanel: dark message area with themed welcome state
- ExecuteDialog: dark modal with primary button styling
- ConfigImporter: dark tabs, inputs, and file upload zone
- TemplateSelector: dark cards with category pills and hover effects

Setup Page Integration:
- Add Configuration/Canvas Builder tab switcher
- Canvas tab renders AtomizerCanvas full-height
- Tabs styled to match Atomaster theme

Build: Passes TypeScript and Vite build

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

atomizer-dashboard/frontend/src/pages/Setup.tsx

@@ -19,12 +19,15 @@ import {
   Info,
   FileBox,
   FolderOpen,
-  File
+  File,
+  Layout,
+  Grid3X3
 } from 'lucide-react';
 import { useStudy } from '../context/StudyContext';
 import { Card } from '../components/common/Card';
 import { Button } from '../components/common/Button';
 import { apiClient, ModelFile } from '../api/client';
+import { AtomizerCanvas } from '../components/canvas/AtomizerCanvas';
 
 interface StudyConfig {
   study_name: string;
@@ -71,9 +74,12 @@ interface StudyConfig {
   }[];
 }
 
+type TabType = 'config' | 'canvas';
+
 export default function Setup() {
   const navigate = useNavigate();
   const { selectedStudy, isInitialized } = useStudy();
+  const [activeTab, setActiveTab] = useState<TabType>('config');
   const [config, setConfig] = useState<StudyConfig | null>(null);
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
@@ -248,8 +254,59 @@ export default function Setup() {
     return acc * 1000; // Approximate for continuous
   }, 1) || 0;
 
+  // Canvas tab - full height
+  if (activeTab === 'canvas') {
+    return (
+      <div className="w-full h-full flex flex-col">
+        {/* Tab Bar */}
+        <div className="flex items-center gap-2 mb-4 border-b border-dark-700 pb-4">
+          <button
+            onClick={() => setActiveTab('config')}
+            className="flex items-center gap-2 px-4 py-2 rounded-lg transition-colors bg-dark-800 text-dark-300 hover:text-white hover:bg-dark-700"
+          >
+            <Layout className="w-4 h-4" />
+            Configuration
+          </button>
+          <button
+            onClick={() => setActiveTab('canvas')}
+            className="flex items-center gap-2 px-4 py-2 rounded-lg transition-colors bg-primary-600 text-white"
+          >
+            <Grid3X3 className="w-4 h-4" />
+            Canvas Builder
+          </button>
+          <div className="flex-1" />
+          <span className="text-dark-400 text-sm">
+            {selectedStudy?.name || 'Study'}
+          </span>
+        </div>
+        {/* Canvas - takes remaining height */}
+        <div className="flex-1 min-h-0 rounded-lg overflow-hidden border border-dark-700">
+          <AtomizerCanvas />
+        </div>
+      </div>
+    );
+  }
+
   return (
     <div className="w-full">
+      {/* Tab Bar */}
+      <div className="flex items-center gap-2 mb-4">
+        <button
+          onClick={() => setActiveTab('config')}
+          className="flex items-center gap-2 px-4 py-2 rounded-lg transition-colors bg-primary-600 text-white"
+        >
+          <Layout className="w-4 h-4" />
+          Configuration
+        </button>
+        <button
+          onClick={() => setActiveTab('canvas')}
+          className="flex items-center gap-2 px-4 py-2 rounded-lg transition-colors bg-dark-800 text-dark-300 hover:text-white hover:bg-dark-700"
+        >
+          <Grid3X3 className="w-4 h-4" />
+          Canvas Builder
+        </button>
+      </div>
+
       {/* Header */}
       <header className="mb-6 flex items-center justify-between border-b border-dark-600 pb-4">
         <div>