feat: Add Q&A Agent app for Issue #254

[SeasonPilot]

When submitting a PR, please confirm the following points and put [x] in the boxes one by one. | 在提出pr时，请确认了以下几点，并逐一使用[x]符号确认勾选。

Checklist | 检查项

• I have read and understood the contributor guidelines. | 我已阅读并理解贡献者指南 。
• I have checked for any duplicate features related to this request and communicated with the project maintainers. | 我已检查没有与此请求重复的功能并与项目维护者进行了沟通。
• I accept the suggestion of the maintainers to make changes to or close this PR. | 我接受此PR配合维护人员的建议进行修改或关闭。
• I have submitted the test files and can provide screenshots of the test results (required for feature or bug fixes) | 我已经提交了测试文件并可提供测试结果截图(功能修改、BUG修复类PR必须提供，其他按需)
• I have added or modified the documentation related to this PR | 我已经添加或修改了本次pr对应的文档说明(非必要，根据实际PR内容按需添加)
• I have added examples and notes if needed | 我已经添加了使用案例代码与文档说明(非必要，根据实际PR内容按需添加)

Please fill in the specific details of this PR: | 请详细填写本次PR的内容:

• Add Simple Q&A Agent application as a minimal demonstration of agentUniverse framework for Issue Sample Apps Submission/案例提供 #254
• 为 Issue Sample Apps Submission/案例提供 #254 添加简单问答智能体应用，作为 agentUniverse 框架的极简演示
• Implement a complete yet minimal agent with bilingual documentation (English/Chinese)
• 实现一个完整但极简的智能体，包含双语文档（英文/中文）
• Include three usage modes: web server, Python API, and interactive testing
• 包含三种使用模式：Web服务器、Python API 和交互式测试
• Provide comprehensive bilingual comments and documentation for educational purposes
• 提供全面的双语注释和文档，用于教学目的
• Use ReAct agent template with Qwen 2.5 LLM (configurable for other LLMs)
• 使用 ReAct 智能体模板和通义千问 2.5（可配置为其他LLM）
• Total 19 files with 1,102 lines of code and documentation
• 共19个文件，包含1,102行代码和文档

Please provide the path of test files and submit screenshots or files of the test results(fill in as needed): | 请填写测试文件路径并提供测试结果截图或文件(按需填写):

• Test file path | 测试文件路径: examples/sample_apps/simple_qa_agent_app/intelligence/test/simple_qa_agent_test.py
• Test includes both automated tests and interactive mode | 测试包含自动化测试和交互模式
• To run tests | 运行测试:

  cd examples/sample_apps/simple_qa_agent_app
  python intelligence/test/simple_qa_agent_test.py

• Interactive mode | 交互模式:
  python intelligence/test/simple_qa_agent_test.py -i
• Web server test | Web服务器测试:
  python bootstrap/intelligence/server_application.py

Then test with curl or API client

curl -X POST http://localhost:8888/agent_run
-H "Content-Type: application/json"
-d '{"agent_name": "simple_qa_agent", "input": "What is AI?"}'

Please list the names of the docs that were added or modified in this PR (fill in as needed): | 请列出本次PR新增或修改的文档名称(按需填写):

• examples/sample_apps/simple_qa_agent_app/README.md - Comprehensive bilingual documentation (431 lines) | 全面的双语文档（431行）
  • Installation and setup guide | 安装和设置指南
  • Three usage methods with examples | 三种使用方法及示例
  • Customization guide | 自定义指南
  • Troubleshooting section | 故障排除部分
  • Architecture explanation | 架构说明
• Inline comments in all configuration files (YAML and TOML) | 所有配置文件中的内联注释（YAML和TOML）
  • config/config.toml - Application configuration | 应用配置
  • config/log_config.toml - Logging configuration | 日志配置
  • config/custom_key.toml - API keys template | API密钥模板
  • intelligence/agentic/agent/agent_instance/simple_qa_agent.yaml - Agent definition | 智能体定义
  • intelligence/agentic/llm/qwen_llm.yaml - LLM configuration | LLM配置
  • intelligence/agentic/prompt/simple_qa_prompt.yaml - Prompt template | 提示词模板
• Python file docstrings and comments | Python文件的文档字符串和注释
  • bootstrap/intelligence/server_application.py - Application entry point | 应用入口点
  • intelligence/test/simple_qa_agent_test.py - Test script with usage examples | 带使用示例的测试脚本

[SeasonPilot]

#254