docs: restructure README and organize docs into subdirectories

- Slim down README from ~400 lines to ~140 lines, keeping only essential content
- Reorganize docs/ into guide/, features/, reference/, images/ subdirectories
- Add GitHub badges (stars, forks, issues, PRs, license, language switch)
- Extract env vars, FAQ, fixes, project structure, global usage into separate docs
- Add LICENSE file (educational and research use only)
- Update all cross-references and issue template links

.github/ISSUE_TEMPLATE/question.md

@@ -9,7 +9,7 @@ assignees: ''
 ## ⚠️ 提交前确认  
 <!-- 请确认以下事项 -->  
 - [ ] 我已经仔细阅读了 [README 常见问题](https://github.com/NanmiCoder/cc-haha#常见问题) 部分
-- [ ] 我已经阅读了[第三方模型使用指南](https://github.com/NanmiCoder/cc-haha/blob/main/docs/third-party-models.md)
+- [ ] 我已经阅读了[第三方模型使用指南](https://github.com/NanmiCoder/cc-haha/blob/main/docs/guide/third-party-models.md)
 - [ ] 我已经搜索并查看了[已关闭的 issues](https://github.com/NanmiCoder/cc-haha/issues?q=is%3Aissue+is%3Aclosed)  
 
 ## ❓ 问题描述