Add .gitignore for repository

- Ignore macOS .DS_Store files
- Ignore Python cache and build artifacts
- Ignore virtual environment directories
- Ignore IDE configuration files

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,43 @@
+# macOS
+.DS_Store
+**/.DS_Store
+
+# Python
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+
+# Virtual Environment
+venv/
+ENV/
+env/
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# Data artifacts (generated files)
+data/prepared_dataset.json
+
+# Upload scripts (optional, kept for convenience)
+# upload_*.py