Refactor UI theme settings in webapp_zh.py

[randomNaming]

• Removed explicit theme setting in Blocks initialization.
• Restored theme setting in app launch method.
• Removed unnecessary copy button from question input.

修复背景与环境
在 Python 3.10 环境下使用 Gradio 6.0 构建 OWL 多智能体协作系统的 Web 界面时，启动出现兼容性错误，导致应用无法正常启动。
问题分析与修复理由
问题 1：show_copy_button 参数不兼容
原因：在代码第 1070 行的 gr.Textbox() 中使用了 show_copy_button=True，但当前 Gradio 版本（可能低于支持的版本）的 Textbox 组件不接收该参数。
错误信息：TypeError: Textbox.init() got an unexpected keyword argument 'show_copy_button'
修复：移除该参数。show_copy_button 在较新版本才支持，当前环境不支持，移除不影响核心功能。
问题 2：theme 参数位置不符合 Gradio 6.0 规范
原因：Gradio 6.0 将 theme 参数从 gr.Blocks() 构造函数移至 app.launch()。
错误信息：UserWarning: The parameters have been moved from the Blocks constructor to the launch() method in Gradio 6.0: theme
修复：将 theme=gr.themes.Soft(primary_hue="blue") 从 gr.Blocks() 移至 app.launch()，符合 6.0 的 API 变更。

Fix Background and Environment
When building the OWL multi-agent collaboration system web interface using Gradio 6.0 under Python 3.10, compatibility errors occurred during startup, preventing the application from launching normally.
Issue Analysis and Fix Rationale
Issue 1: show_copy_button Parameter Incompatibility
Root Cause: The code at line 1070 used show_copy_button=True in gr.Textbox(), but the current Gradio version (possibly older than the version that supports this parameter) does not accept this parameter in the Textbox component.
Error Message: TypeError: Textbox.init() got an unexpected keyword argument 'show_copy_button'
Fix Rationale: This parameter is supported in newer Gradio versions but not in the current environment. Removing it doesn't affect core functionality, and the text input works normally without this feature.
Issue 2: theme Parameter Location Non-compliance with Gradio 6.0 Specification
Root Cause: Gradio 6.0 moved the theme parameter from the gr.Blocks() constructor to the app.launch() method as part of an API change.
Error Message: UserWarning: The parameters have been moved from the Blocks constructor to the launch() method in Gradio 6.0: theme
Fix Rationale: Moving theme=gr.themes.Soft(primary_hue="blue") from gr.Blocks() to app.launch() aligns with Gradio 6.0's API changes, ensuring correct theme application and eliminating warnings.
Summary of Fixes
Removed the show_copy_button=True parameter (line 1070)
Moved the theme parameter from gr.Blocks() to app.launch() (lines 845 and 1275)
After these fixes, the application can start and run normally in the Python 3.10 + Gradio 6.0 environment.

[Aaron617]

Thanks we will review this pr

[zjrwtx]

thanks @randomNaming ,lets merge this into this pr:
randomNaming#1
cc @Aaron617