migrate 392 questions to pattern format

backend/data/questions/binary-tree-paths.yaml

@@ -8,9 +8,12 @@ categories:
   - strings
   - recursion
 patterns:
-  - dfs
-  - backtracking
-  - tree-traversal
+  - slug: dfs
+    is_optimal: true
+  - slug: backtracking
+    is_optimal: false
+  - slug: tree-traversal
+    is_optimal: false
 
 function_signature: "def binary_tree_paths(root: TreeNode) -> list[str]:"