chore: comprehensive .gitignore for user/contributor experience

UPDATED .gitignore WITH:

✅ Python Core - __pycache__, *.pyc, etc.
✅ Build & Distribution - build/, dist/, eggs/
✅ Virtual Environments - venv/, .venv/
✅ IDE & Editors - .vscode/, .idea/, *.swp
✅ Testing & Coverage - .pytest_cache/, .coverage/
✅ Type Checking - .mypy_cache/
✅ Jupyter - .ipynb_checkpoints/
✅ Logs & Debug - *.log, debug/
✅ Database - *.db, *.sqlite
✅ Machine Learning - *.h5, *.pkl, *.pth
✅ Data Files - data/*.csv, data/*.json
✅ OS & System - .DS_Store, Thumbs.db
✅ Temporary Files - tmp/, temp/, *.tmp
✅ Scripts (Bulk) - scripts/create_*.py
✅ Issue Generation - issue_*.txt, *_log.txt
✅ Auto-Generated Docs - docs/generated/
✅ Analysis Files - *_ANALYSIS*.md, *_SUMMARY*.md
✅ GitHub Internal - .github/ISSUES/NEW_*/
✅ Notes & Personal - NOTES.md, scratch.py
✅ Secrets & Credentials - *.pem, *.key, *.secret
✅ API Keys & Tokens - *.token, *.api_key

REMOVED FROM TRACKING:
- 100_PERCENT_ISSUE_QUALITY_ACHIEVED.md
- 250_ISSUES_COMPLETE.md
- DUPLICATE_CLEANUP_COMPLETE.md
- scripts/ directory

RESULT:
- Clean repository for users/contributors
- Only essential files tracked
- No temporary/generated files
- Better contributor experience

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

Author: hackdartstorm