style(webui): 布局对齐美观调整

1. html_center margin:100→8px 0
   修复板块标题上下100px巨大空白, 改为紧凑8px, 整体视觉更聚合
   (影响所有用 html_center 的板块标题: 模型切换/参考信息/目标文本等)

2. 模型切换板块两行 scale 统一总宽28:
   Row1: 模型名(20)+刷新模型列表(8) = 28
   Row2: GPT(10)+SoVITS(10)+刷新模型路径(8) = 28
   (原 Row1=21+7=28, Row2=14+14+14=42 不一致; 现两行等宽对齐)

验证: WebUI启动正常, margin:8px 0 生效, 端到端功能不受影响。

GPT_SoVITS/inference_webui.py

@@ -1194,7 +1194,7 @@ def process_text(texts):
 
 
 def html_center(text, label="p"):
-    return f"""<div style="text-align: center; margin: 100; padding: 50;">
+    return f"""<div style="text-align: center; margin: 8px 0; padding: 4px 0;">
                 <{label} style="margin: 0; padding: 0;">{text}</{label}>
                 </div>"""
 
@@ -1453,25 +1453,25 @@ with gr.Blocks(title="GPT-SoVITS WebUI", analytics_enabled=False, js=js, css=css
                 choices=[],
                 value="",
                 interactive=True,
-                scale=21,
+                scale=20,
             )
-            refresh_models_btn = gr.Button(i18n("刷新模型列表"), variant="primary", scale=7)
+            refresh_models_btn = gr.Button(i18n("刷新模型列表"), variant="primary", scale=8)
         with gr.Row():
             GPT_dropdown = gr.Dropdown(
                 label=i18n("GPT模型列表"),
                 choices=sorted(GPT_names, key=custom_sort_key),
                 value=gpt_path,
                 interactive=True,
-                scale=14,
+                scale=10,
             )
             SoVITS_dropdown = gr.Dropdown(
                 label=i18n("SoVITS模型列表"),
                 choices=sorted(SoVITS_names, key=custom_sort_key),
                 value=sovits_path,
                 interactive=True,
-                scale=14,
+                scale=10,
             )
-            refresh_button = gr.Button(i18n("刷新模型路径"), variant="primary", scale=14)
+            refresh_button = gr.Button(i18n("刷新模型路径"), variant="primary", scale=8)
             refresh_button.click(fn=change_choices, inputs=[], outputs=[SoVITS_dropdown, GPT_dropdown])
     with gr.Group():
         gr.Markdown(html_center(i18n("*请上传并填写参考信息"), "h3"))