chore: add temporary files to .gitignore and clean up repository

CLEANUP PERFORMED:

✅ Updated .gitignore to exclude:
  - Issue creation scripts (create_*.py, scripts/create_*.py)
  - Issue logs and outputs (*_log.txt, *.txt)
  - Temporary analysis files (*_ANALYSIS*.md, *_SUMMARY*.md)
  - Generated issue files (.github/ISSUES/NEW_*/)
  - Backup files (*.bak, *.backup, *.old)
  - Temporary directories (tmp/, temp/)
  - Shell scripts for bulk operations (*.sh)
  - Automation scripts (automation/, tools/bulk_*.py)

✅ Removed from git tracking:
  - .github/ISSUES/NEW_250/ (5 files)
  - .github/ISSUES/250_NEW_ISSUES_PLAN.md
  - ISSUE_ANALYSIS_AND_PLAN.md
  - basic_issues_log.txt
  - create_250_issues.py
  - create_expert_issues.py
  - create_more_issues.py
  - issue_creation_log.txt

✅ Deleted temporary files:
  - All create_*.py scripts
  - All *_log.txt files
  - All temporary markdown files

RESULT:
- Repository is now clean
- Only essential files tracked
- Temporary files ignored
- Contributors won't see unnecessary files

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

Author: hackdartstorm