feat: quick wins - dockerignore, env secrets, gzip, cache-control

- Add .dockerignore to exclude .git, __pycache__, docs, etc. from Docker context
- Create .env.example template with documented env vars
- Move OBSIGATE_ADMIN_PASSWORD from docker-compose.yml to env_file: .env
- Add .env.* to .gitignore (excluding .env.example)
- Enable GZipMiddleware for ~70% bandwidth reduction on text responses
- Add Cache-Control: immutable for /static/ assets
- Update ROADMAP: mark all 4 quick wins as done, add audit findings
- Add comprehensive technical audit report (AUDIT_TECHNIQUE_2026-05-27.md)

.gitignore

@@ -2,6 +2,8 @@ __pycache__/
 *.pyc
 *.pyo
 .env
+.env.*
+!.env.example
 test_vault/
 .venv/
 venv/