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/requirements.txt

@@ -0,0 +1,16 @@
+fastapi>=0.115.0,<1
+uvicorn[standard]>=0.32.0,<1
+sqlalchemy>=2.0.36,<3
+alembic>=1.14.0,<2
+psycopg2-binary>=2.9.10,<3
+pydantic>=2.10.0,<3
+pydantic-settings>=2.6.0,<3
+python-multipart>=0.0.17,<1
+jsonschema>=4.23.0,<5
+passlib[bcrypt]>=1.7.4,<2
+python-jose[cryptography]>=3.3.0,<4
+httpx>=0.28.0,<1
+
+# dev
+pytest>=8.3.0,<9
+pytest-asyncio>=0.24.0,<1