Add multilingual exercise code (#1959)

Replace the exercise pages' Python-only snippets with source-backed implementations for the 13 visible programming languages, and localize reader-facing comments by site language. Zig remains out of scope.

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codes/kotlin/chapter_divide_and_conquer/fast_power.kt

@@ -0,0 +1,25 @@
+/**
+ * File: fast_power.kt
+ * Created Time: 2026-08-18
+ * Author: Hello Algo Team
+ */
+
+package chapter_divide_and_conquer.fast_power
+
+/* 快速幂 */
+fun fastPow(x: Int, n: Int): Int {
+    if (n == 0) {
+        return 1
+    }
+    val half = fastPow(x, n / 2)
+    if (n % 2 == 0) {
+        return half * half
+    }
+    return half * half * x
+}
+
+fun main() {
+    check(fastPow(7, 0) == 1)
+    check(fastPow(3, 5) == 243)
+    check(fastPow(2, 6) == 64)
+}