fix(lemonade): use configured api_key instead of hardcoded value

The Lemonade provider ignores the api_key parameter and always uses
the hardcoded string 'lemonade'. This prevents authentication when
Lemonade Server is configured with a custom API key via LEMONADE_API_KEY.

Fixes #25363

Signed-off-by: bahtya <bahtyar153@qq.com>

litellm/llms/lemonade/chat/transformation.py

@@ -111,7 +111,11 @@ class LemonadeChatConfig(OpenAILikeChatConfig):
             or "http://localhost:8000/api/v1"
         )  # type: ignore
         # Lemonade doesn't check the key
-        key = "lemonade"
+        key = (
+            api_key
+            or get_secret_str("LEMONADE_API_KEY")
+            or "lemonade"
+        )
         return api_base, key
 
     def transform_response(