feat(canvas): Auto-load optimization config from study

Phase 3 of Canvas Professional Upgrade:
- Fix ConfigImporter API endpoint URL (/api/optimization/studies/...)
- Add currentStudyId prop to auto-select study in importer
- Parse response correctly (data.config instead of raw response)
- Replace file upload emoji with FolderOpen Lucide icon
- Add "Load Study Config" button to Setup canvas tab header
- Show button only when canvas is empty

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

atomizer-dashboard/frontend/src/components/canvas/panels/ConfigImporter.tsx

@@ -7,16 +7,18 @@
  * - Load from study directory
  */
 
-import { useState, useRef } from 'react';
+import { useState, useRef, useEffect } from 'react';
+import { FolderOpen } from 'lucide-react';
 import { useCanvasStore, OptimizationConfig } from '../../../hooks/useCanvasStore';
 
 interface ConfigImporterProps {
   isOpen: boolean;
   onClose: () => void;
   onImport: (source: string) => void;
+  currentStudyId?: string; // Auto-load this study when provided
 }
 
-export function ConfigImporter({ isOpen, onClose, onImport }: ConfigImporterProps) {
+export function ConfigImporter({ isOpen, onClose, onImport, currentStudyId }: ConfigImporterProps) {
   const [tab, setTab] = useState<'file' | 'paste' | 'study'>('file');
   const [jsonText, setJsonText] = useState('');
   const [studyPath, setStudyPath] = useState('');
@@ -26,6 +28,14 @@ export function ConfigImporter({ isOpen, onClose, onImport }: ConfigImporterProp
 
   const { loadFromConfig } = useCanvasStore();
 
+  // Set study path from current study when provided
+  useEffect(() => {
+    if (currentStudyId) {
+      setStudyPath(currentStudyId);
+      setTab('study');
+    }
+  }, [currentStudyId, isOpen]);
+
   if (!isOpen) return null;
 
   const handleFileSelect = async (e: React.ChangeEvent<HTMLInputElement>) => {
@@ -69,13 +79,14 @@ export function ConfigImporter({ isOpen, onClose, onImport }: ConfigImporterProp
 
     try {
       // Call backend API to load study config
-      const response = await fetch(`/api/studies/${encodeURIComponent(studyPath)}/config`);
+      const response = await fetch(`/api/optimization/studies/${encodeURIComponent(studyPath)}/config`);
 
       if (!response.ok) {
         throw new Error(`Study not found: ${studyPath}`);
       }
 
-      const config = await response.json() as OptimizationConfig;
+      const data = await response.json();
+      const config = data.config as OptimizationConfig;
       validateConfig(config);
       loadFromConfig(config);
       onImport(`Study: ${studyPath}`);
@@ -165,7 +176,7 @@ export function ConfigImporter({ isOpen, onClose, onImport }: ConfigImporterProp
                 disabled={isLoading}
                 className="w-full py-8 border-2 border-dashed border-dark-600 rounded-lg hover:border-primary-500/50 hover:bg-dark-800 transition-colors flex flex-col items-center gap-2"
               >
-                <span className="text-3xl">📁</span>
+                <FolderOpen size={32} className="text-primary-400" />
                 <span className="text-dark-300">
                   {isLoading ? 'Loading...' : 'Click to select file'}
                 </span>