refactor: uv-based deps, no nexus auth, LLM retries, lock cleanup, health checks, e2e tests

tests/conftest.py

@@ -12,8 +12,6 @@ sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
 
 os.environ["DATABASE_PATH"] = ":memory:"
 os.environ["NEXUS_URL"] = "http://nexus:8081"
-os.environ["NEXUS_USERNAME"] = "admin"
-os.environ["NEXUS_PASSWORD"] = "admin123"
 os.environ["LOG_SYSLOG_HOST"] = ""
 os.environ["TEMP_DIR"] = "/tmp/guarddog-nexus-test"