migrate 392 questions to pattern format

backend/data/questions/target-sum.yaml

@@ -7,8 +7,10 @@ categories:
   - arrays
   - dynamic-programming
 patterns:
-  - dynamic-programming
-  - backtracking
+  - slug: dynamic-programming
+    is_optimal: true
+  - slug: backtracking
+    is_optimal: false
 
 function_signature: "def find_target_sum_ways(nums: list[int], target: int) -> int:"