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/charts/NivoParallelCoordinates.tsx

@@ -91,7 +91,7 @@ function getAvailableParams(trials: Trial[]): string[] {
 
 export function NivoParallelCoordinates({
   trials,
-  objectives,
+  objectives: _objectives,
   designVariables,
   paretoFront = [],
   height = 400