migrate 392 questions to pattern format

backend/data/questions/add-to-array-form-of-integer.yaml

@@ -7,7 +7,8 @@ categories:
   - arrays
   - math
 patterns:
-  - two-pointers
+  - slug: two-pointers
+    is_optimal: true
 
 function_signature: "def add_to_array_form(num: list[int], k: int) -> list[int]:"