migrate 392 questions to pattern format

backend/data/questions/redundant-connection.yaml

@@ -6,8 +6,10 @@ leetcode_url: https://leetcode.com/problems/redundant-connection/
 categories:
   - graphs
 patterns:
-  - union-find
-  - dfs
+  - slug: union-find
+    is_optimal: true
+  - slug: dfs
+    is_optimal: false
 
 function_signature: "def find_redundant_connection(edges: list[list[int]]) -> list[int]:"