feat: backend ingest API, Docker Compose, Ubuntu install guide

- FastAPI: POST /api/v1/events, GET /health, JSON Schema validation

- PostgreSQL models, Alembic migration, bootstrap API key

- deploy/docker-compose.yml, .env.example

- docs/install-ubuntu-24.04.md, updated work-plan (agents first)

backend/app/api/v1/router.py

@@ -0,0 +1,7 @@
+from fastapi import APIRouter
+
+from app.api.v1 import events, health
+
+api_router = APIRouter()
+api_router.include_router(health.router)
+api_router.include_router(events.router)