Re-translate the Japanese version (#1871)

* Retranslate Japanese docs with GPT-5.4

* Retranslate Japanese code with GPT-5.4

ja/codes/java/chapter_dynamic_programming/climbing_stairs_dfs.java

@@ -7,9 +7,9 @@
 package chapter_dynamic_programming;
 
 public class climbing_stairs_dfs {
-    /* 探索 */
+    /* 検索 */
     public static int dfs(int i) {
-        // 既知の dp[1] と dp[2] を返す
+        // 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]
@@ -26,6 +26,6 @@ public class climbing_stairs_dfs {
         int n = 9;
 
         int res = climbingStairsDFS(n);
-        System.out.println(String.format("%d段の階段を登る解は%d通りです", n, res));
+        System.out.println(String.format("%d 段の階段の登り方は全部で %d 通り", n, res));
     }
-}
+}