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.

tests/tools/fixtures/azdo_trigger_pipeline.json

@@ -0,0 +1,11 @@
+{
+  "id": 1001,
+  "buildNumber": "20240115.1",
+  "status": "notStarted",
+  "queueTime": "2024-01-15T10:00:00Z",
+  "definition": {
+    "id": 10,
+    "name": "Release Pipeline"
+  },
+  "sourceBranch": "refs/heads/main"
+}