Add --no-ui flag to server command to reduce idle CPU usage (#824)

Gradio's internal queue and polling mechanism runs continuously even
when the server is idle, causing constant ~7% CPU usage. The new
--no-ui flag skips mounting the Gradio interface and runs the FastAPI
app directly, bringing idle CPU back to near 0%.

Author: danielgatis

README.md

@@ -184,6 +184,12 @@ rembg s --host 0.0.0.0 --port 7000 --log_level info
 
 For complete API documentation, visit: `http://localhost:7000/api`
 
+**Disable the Gradio UI (reduces idle CPU usage):**
+
+```shell
+rembg s --no-ui
+```
+
 **Remove background from an image URL:**
 
 ```shell

rembg/commands/s_command.py

@@ -55,7 +55,14 @@
     show_default=True,
     help="number of worker threads",
 )
-def s_command(port: int, host: str, log_level: str, threads: int) -> None:
+@click.option(
+    "--no-ui",
+    is_flag=True,
+    default=False,
+    show_default=True,
+    help="disable the Gradio UI (reduces idle CPU usage)",
+)
+def s_command(port: int, host: str, log_level: str, threads: int, no_ui: bool) -> None:
     """
     Command-line interface for running the FastAPI web server.
 
@@ -323,8 +330,11 @@ def inference(input_path, model, *args):
     print(
         f"To access the API documentation, go to http://{'localhost' if host == '0.0.0.0' else host}:{port}/api"
     )
-    print(
-        f"To access the UI, go to http://{'localhost' if host == '0.0.0.0' else host}:{port}"
-    )
+    if not no_ui:
+        print(
+            f"To access the UI, go to http://{'localhost' if host == '0.0.0.0' else host}:{port}"
+        )
 
-    uvicorn.run(gr_app(app), host=host, port=port, log_level=log_level)
+    uvicorn.run(
+        app if no_ui else gr_app(app), host=host, port=port, log_level=log_level
+    )