add integration tests with Docker Compose

[Giuseppe552]

Currently all 141 tests are unit tests against mocked data. No integration tests run the full stack (Neo4j + Redis + worker).

Goal: A test:integration script that:

1. Spins up Neo4j + Redis via Docker Compose
2. Runs a real scan against a test target (e.g., example.com)
3. Verifies nodes/edges were written to Neo4j
4. Tears down containers

Could use the existing docker-compose.yml with a test profile.