Fix voice recording page freeze: upload-only for custom voice

Gradio's in-browser microphone freezes the page on stop-recording due to
client-side audio encoding. Switch to upload-only so users record on their
phone/voice memo app and upload the file — same cloning result, no freeze.

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

ui/layout.py

@@ -542,9 +542,9 @@ def create_layout(load_sample_fn=None, create_book_fn=None):
                     elem_classes=["field", "theme-pick"],
                 )
                 custom_voice_audio = gr.Audio(
-                    sources=["microphone", "upload"],
+                    sources=["upload"],
                     type="filepath",
-                    label="Record or upload your voice (5–60 s of clear speech)",
+                    label="Upload a voice recording (5–60 s of clear speech — record on your phone, then upload)",
                     visible=False,
                     elem_classes=["custom-voice-field"],
                 )