feat: update requirements and enhance task guide UI

- Added core dependencies for file handling (Pillow, openpyxl, python-docx, PyPDF2, chardet) to requirements.txt.
- Modified SandboxRunner to create a dedicated codes directory for task scripts.
- Expanded prompts.py with a list of allowed libraries for code generation.
- Simplified the task guide UI by removing drag-and-drop functionality and enhancing layout and styling for better user experience.

requirements.txt

@@ -4,6 +4,13 @@
 # conda activate localagent
 # pip install -r requirements.txt
 
+# 核心依赖
 python-dotenv>=1.0.0
 requests>=2.31.0
 
+# 文件处理库（代码生成可用）
+Pillow>=10.0.0          # 图片处理
+openpyxl>=3.1.0         # Excel 处理
+python-docx>=1.0.0      # Word 文档处理
+PyPDF2>=3.0.0           # PDF 处理
+chardet>=5.0.0          # 文件编码检测