feat: add Spanish greeting

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app.py

@@ -1,9 +1,12 @@
 def greet(name: str, lang: str = "en") -> str:
     if lang == "zh":
         return f"你好,{name}!"
+    if lang == "es":
+        return f"¡Hola, {name}!"
     return f"Hello, {name}!"
 
 
 if __name__ == "__main__":
     print(greet("world"))
     print(greet("世界", lang="zh"))
+    print(greet("mundo", lang="es"))