Add type hints to infer for MCP compatibility

Gradio uses type hints to generate MCP schema (at /gradio_api/mcp/schema) that MCP clients use to get tool desc and arg type and desc

app.py

@@ -25,16 +25,16 @@ MAX_IMAGE_SIZE = 1024
 
 @spaces.GPU(duration=65)
 def infer(
-    prompt,
-    negative_prompt="",
-    seed=42,
-    randomize_seed=False,
-    width=1024,
-    height=1024,
-    guidance_scale=1.5,
-    num_inference_steps=8,
-    progress=gr.Progress(track_tqdm=True),
-):
+    prompt: str,
+    negative_prompt: str = "",
+    seed: int = 42,
+    randomize_seed: bool = False,
+    width: int = 1024,
+    height: int = 1024,
+    guidance_scale: float = 1.5,
+    num_inference_steps: int = 8,
+    progress: gr.Progress = gr.Progress(track_tqdm=True),
+) -> tuple["PIL.Image.Image", int]:
     """Generate an image using Stable Diffusion 3.5 Large TurboX.
     
     Args: