Re-translate the Japanese version (#1871)

* Retranslate Japanese docs with GPT-5.4

* Retranslate Japanese code with GPT-5.4

ja/codes/swift/chapter_dynamic_programming/climbing_stairs_dfs.swift

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+/**
+ * File: climbing_stairs_dfs.swift
+ * Created Time: 2023-07-15
+ * Author: nuomi1 (nuomi1@qq.com)
+ */
+
+/* 検索 */
+func dfs(i: Int) -> Int {
+    // 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]
+    let count = dfs(i: i - 1) + dfs(i: i - 2)
+    return count
+}
+
+/* 階段登り：探索 */
+func climbingStairsDFS(n: Int) -> Int {
+    dfs(i: n)
+}
+
+@main
+enum ClimbingStairsDFS {
+    /* Driver Code */
+    static func main() {
+        let n = 9
+
+        let res = climbingStairsDFS(n: n)
+        print("\(n) 段の階段を上る方法は全部で \(res) 通り")
+    }
+}