feat: add E2E test suite with nightly CI, fix dashboard Dockerfile

E2E Tests:
- 17 integration tests covering: health, repos CRUD, findings lifecycle,
  cascade delete (SAST + DAST + pentest), DAST targets, stats overview
- TestServer harness: spins up agent API on random port with isolated
  MongoDB database per test, auto-cleanup
- Added lib.rs to expose agent internals for integration tests
- Nightly CI workflow with MongoDB service container (3 AM UTC)

Tests verify:
- Repository add/list/delete + duplicate rejection + invalid ID handling
- Finding creation, filtering by severity/repo, status updates, bulk updates
- Cascade delete: repo deletion removes all DAST targets, pentest sessions,
  attack chain nodes, DAST findings, SAST findings, and SBOM entries
- DAST target CRUD and empty finding list
- Stats overview accuracy with zero and populated data

Also:
- Fix Dockerfile.dashboard: bump dioxus-cli 0.7.3 → 0.7.4 (compile fix)
- Fix clippy: allow new_without_default for pattern scanners

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

compliance-agent/Cargo.toml

@@ -42,3 +42,14 @@ tokio-tungstenite = { version = "0.26", features = ["rustls-tls-webpki-roots"] }
 futures-core = "0.3"
 dashmap = { workspace = true }
 tokio-stream = { workspace = true }
+
+[dev-dependencies]
+compliance-core = { workspace = true, features = ["mongodb"] }
+reqwest = { workspace = true }
+serde_json = { workspace = true }
+tokio = { workspace = true }
+mongodb = { workspace = true }
+uuid = { workspace = true }
+secrecy = { workspace = true }
+axum = "0.8"
+tower-http = { version = "0.6", features = ["cors"] }