Fix Gradio 6.0 API breakage on HF Spaces

- Image() no longer accepts show_download_button; remove it.
- theme/css moved off Blocks(...) to launch() in Gradio 6.0;
detect gr.__version__ and route accordingly so the file still
works under Gradio 4.x (local dev) and Gradio 6.x (HF Space).

app.py

@@ -564,7 +564,21 @@ HERO_HTML = """
 </div>
 """
 
-with gr.Blocks(title="OneVision Encoder Codec View", theme=THEME, css=CUSTOM_CSS) as demo:
+try:
+    _GR_MAJOR = int(gr.__version__.split(".")[0])
+except Exception:
+    _GR_MAJOR = 4
+_BLOCK_KW: dict = {"title": "OneVision Encoder Codec View"}
+_LAUNCH_KW: dict = {}
+if _GR_MAJOR >= 6:
+    # In Gradio 6.0 these moved off Blocks(...) onto launch(...).
+    _LAUNCH_KW["theme"] = THEME
+    _LAUNCH_KW["css"] = CUSTOM_CSS
+else:
+    _BLOCK_KW["theme"] = THEME
+    _BLOCK_KW["css"] = CUSTOM_CSS
+
+with gr.Blocks(**_BLOCK_KW) as demo:
     gr.HTML(HERO_HTML)
 
     with gr.Row(equal_height=False):
@@ -643,8 +657,7 @@ with gr.Blocks(title="OneVision Encoder Codec View", theme=THEME, css=CUSTOM_CSS
                     with gr.Group(elem_classes="ovc-card"):
                         gr.Markdown("### Packed canvas")
                         canvas_out = gr.Image(
-                            label="", show_label=False, show_download_button=True,
-                            height=320,
+                            label="", show_label=False, height=320,
                         )
                 with gr.Column(scale=1):
                     with gr.Group(elem_classes="ovc-card"):
@@ -674,4 +687,8 @@ with gr.Blocks(title="OneVision Encoder Codec View", theme=THEME, css=CUSTOM_CSS
 
 
 if __name__ == "__main__":
-    demo.launch(server_name="0.0.0.0", server_port=int(os.environ.get("PORT", 7860)))
+    demo.launch(
+        server_name="0.0.0.0",
+        server_port=int(os.environ.get("PORT", 7860)),
+        **_LAUNCH_KW,
+    )