Implement Undo system for AI and bulk actions

src/App.tsx

@@ -10,6 +10,7 @@ import { getAllSyncedRows, saveRowToSupabase } from './lib/supabase';
 import { getStoredSession, signOut, type AuthSession } from './lib/auth';
 import { LoginPage } from './components/LoginPage';
 import { DimensionsView } from './components/DimensionsView';
+import { UndoToast } from './components/UndoToast';
 
 export default function App() {
   const [session, setSession] = useState<AuthSession | null>(() => getStoredSession());
@@ -31,6 +32,7 @@ export default function App() {
     hasUnsavedChanges: false
   });
   const [activeModule, setActiveModule] = useState<'descriptions' | 'matrix' | 'dimensions'>('descriptions');
+  const [undoState, setUndoState] = useState<{ data: ExcelRow[], message: string } | null>(null);
   const [editingRowIndex, setEditingRowIndex] = useState<number | null>(null);
   const [isLoadingDefault, setIsLoadingDefault] = useState(true);
   const [defaultLoadError, setDefaultLoadError] = useState<string | null>(null);
@@ -245,6 +247,23 @@ export default function App() {
     }
   };
 
+  const captureState = (message: string) => {
+    setUndoState({
+      data: JSON.parse(JSON.stringify(appState.data)), // Deep copy
+      message
+    });
+  };
+
+  const handleUndo = () => {
+    if (!undoState) return;
+    setAppState(prev => ({
+      ...prev,
+      data: undoState.data,
+      hasUnsavedChanges: true
+    }));
+    setUndoState(null);
+  };
+
   const stats = useMemo(() => {
     if (appState.data.length === 0) return null;
     let missingDeLong = 0;
@@ -329,6 +348,7 @@ export default function App() {
                   headers={appState.headers}
                   onEdit={(index) => setEditingRowIndex(index)}
                   onSaveRow={handleSaveRow}
+                  onCaptureState={captureState}
                 />
               )}
             </>
@@ -336,12 +356,19 @@ export default function App() {
         </main>
       </div>
 
+      <UndoToast 
+        undoState={undoState} 
+        onUndo={handleUndo} 
+        onClose={() => setUndoState(null)} 
+      />
+
       {editingRowIndex !== null && (
         <EditPanel 
           row={appState.data[editingRowIndex]} 
           rowIndex={editingRowIndex}
           onSave={handleSaveRow}
           onClose={() => setEditingRowIndex(null)}
+          onCaptureState={captureState}
         />
       )}
     </div>