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/App.tsx

@@ -8,6 +8,7 @@ import Dashboard from './pages/Dashboard';
 import Analysis from './pages/Analysis';
 import Insights from './pages/Insights';
 import Results from './pages/Results';
+import CanvasView from './pages/CanvasView';
 
 const queryClient = new QueryClient({
   defaultOptions: {
@@ -27,6 +28,9 @@ function App() {
             {/* Home page - no sidebar layout */}
             <Route path="/" element={<Home />} />
 
+            {/* Canvas page - full screen, no sidebar */}
+            <Route path="canvas" element={<CanvasView />} />
+
             {/* Study pages - with sidebar layout */}
             <Route element={<MainLayout />}>
               <Route path="setup" element={<Setup />} />