feat: initial commit — Billo Release Agent (LangGraph)

LangGraph-based release automation agent with:
- PR discovery (webhook + polling)
- AI code review via Claude Code CLI (subscription-based)
- Auto-create Jira tickets for PRs without ticket ID
- Jira ticket lifecycle management (code review -> staging -> done)
- CI/CD pipeline trigger, polling, and approval gates
- Slack interactive messages with approval buttons
- Per-repo semantic versioning
- PostgreSQL persistence (threads, staging, releases)
- FastAPI API (webhooks, approvals, status, manual triggers)
- Docker Compose deployment

1069 tests, 95%+ coverage.

.gitignore

@@ -0,0 +1,36 @@
+# Environment
+.env
+.env.local
+
+# Python
+__pycache__/
+*.py[cod]
+*.egg-info/
+dist/
+build/
+.eggs/
+
+# Virtual environment
+.venv/
+venv/
+
+# uv
+uv.lock
+
+# IDE
+.idea/
+.vscode/
+*.swp
+*.swo
+
+# Testing
+.coverage
+htmlcov/
+.pytest_cache/
+
+# Data
+data/staging/
+
+# OS
+.DS_Store
+Thumbs.db