migrate 392 questions to pattern format

backend/data/questions/verifying-an-alien-dictionary.yaml

@@ -8,7 +8,8 @@ categories:
   - strings
   - hash-tables
 patterns:
-  - two-pointers
+  - slug: two-pointers
+    is_optimal: true
 
 function_signature: "def is_alien_sorted(words: list[str], order: str) -> bool:"