migrate 392 questions to pattern format

backend/data/questions/additive-number.yaml

@@ -7,7 +7,8 @@ categories:
   - strings
   - recursion
 patterns:
-  - backtracking
+  - slug: backtracking
+    is_optimal: true
 
 function_signature: "def is_additive_number(num: str) -> bool:"