Re-translate the Japanese version (#1871)

* Retranslate Japanese docs with GPT-5.4

* Retranslate Japanese code with GPT-5.4

ja/codes/dart/chapter_dynamic_programming/climbing_stairs_dfs.dart

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+/**
+ * File: climbing_stairs_dfs.dart
+ * Created Time: 2023-08-11
+ * Author: liuyuxin (gvenusleo@gmail.com)
+ */
+
+/* 検索 */
+int dfs(int i) {
+  // dp[1] と dp[2] は既知なので返す
+  if (i == 1 || i == 2) return i;
+  // dp[i] = dp[i-1] + dp[i-2]
+  int count = dfs(i - 1) + dfs(i - 2);
+  return count;
+}
+
+/* 階段登り：探索 */
+int climbingStairsDFS(int n) {
+  return dfs(n);
+}
+
+/* Driver Code */
+void main() {
+  int n = 9;
+
+  int res = climbingStairsDFS(n);
+  print("$n 段の階段の登り方は全部で $res 通り");
+}