- Remove plaintext Ximilar and Perplexity API keys from start-lab.bat
- Remove hardcoded key defaults from lab_api.py, lab_api_backup.py, lab_api_new.py
- start-lab.bat now reads from environment variables or .env file
- Add .env.example with placeholder values
- .env already in .gitignore (confirmed)
- Git history purged of all key values via git-filter-repo
Closes#26