Fix TypeScript build errors

- Remove unused variables (allFolders, getFolderDepth, hasChildren, legacyCategories)
- Fix Lucide icon title prop by wrapping in span elements

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

frontend/src/components/library/AddToFolderMenu.tsx

@@ -38,10 +38,7 @@ export function AddToFolderMenu({ treeId, onFolderCreated }: AddToFolderMenuProp
   const loadFoldersAndAssignments = async () => {
     setIsLoading(true)
     try {
-      const [foldersData, allFolders] = await Promise.all([
-        foldersApi.list(),
-        Promise.resolve([]), // Will load tree's folder assignments below
-      ])
+      const foldersData = await foldersApi.list()
       setFolders(foldersData)
 
       // Check which folders contain this tree