chore(security): drop passlib for direct bcrypt + reject CLI-flag check targets

- Replace passlib.CryptContext with bcrypt 4.2.1 directly (passlib is
  unmaintained and only emitted warnings when paired with bcrypt 4+).
  hash_password / verify_password now call bcrypt.checkpw / .hashpw, and
  verify_password is hardened against empty inputs without raising.
  scripts/hash_password.py + tests/conftest.py updated to match.
- status_checker.check_node() now rejects targets starting with '-' before
  any subprocess invocation, defending ping/tcp paths against arg-injection
  if an admin sets a check_target like '-O'.

Tests added:
- test_auth: expired JWT, malformed JWT, wrong-secret JWT, empty password
  vs empty server hash, verify_password edge cases.
- test_scan: _background_scan failure path marks ScanRun failed, leaves
  non-running terminal status alone, success path invokes run_scan.
- test_status_checker: ping/tcp invocations are bypassed when target or
  ip starts with '-'.

Backend coverage 89% → 90%.

backend/tests/conftest.py

@@ -5,23 +5,21 @@ os.environ.setdefault("SECRET_KEY", "test-only-secret-key-not-for-production")
 
 import pytest
 from httpx import ASGITransport, AsyncClient
-from passlib.context import CryptContext
 from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
 
+from app.core.security import hash_password
 from app.db.database import Base, get_db
 from app.main import app
 
 TEST_DB_URL = "sqlite+aiosqlite:///:memory:"
 
-_pwd_ctx = CryptContext(schemes=["bcrypt"], deprecated="auto")
-
 
 @pytest.fixture(autouse=True, scope="session")
 def test_credentials():
     """Configure test auth credentials directly on settings."""
     from app.core.config import settings
     settings.auth_username = "admin"
-    settings.auth_password_hash = _pwd_ctx.hash("admin")
+    settings.auth_password_hash = hash_password("admin")
 
 
 @pytest.fixture

backend/tests/test_auth.py

@@ -68,3 +68,71 @@ async def test_login_with_malformed_hash_returns_401_not_500(client: AsyncClient
         assert res.status_code == 401
     finally:
         settings.auth_password_hash = original
+
+
+# --- JWT-level cases ---
+
+async def test_expired_token_rejected(client: AsyncClient):
+    """A JWT whose `exp` is in the past must be refused."""
+    from datetime import datetime, timedelta, timezone
+
+    from jose import jwt
+
+    from app.core.config import settings
+    payload = {
+        "sub": "admin",
+        "exp": datetime.now(timezone.utc) - timedelta(minutes=1),
+    }
+    token = jwt.encode(payload, settings.secret_key, algorithm=settings.algorithm)
+    res = await client.get("/api/v1/nodes", headers={"Authorization": f"Bearer {token}"})
+    assert res.status_code == 401
+
+
+async def test_malformed_token_rejected(client: AsyncClient):
+    res = await client.get("/api/v1/nodes", headers={"Authorization": "Bearer not-a-jwt"})
+    assert res.status_code == 401
+
+
+async def test_token_signed_with_wrong_secret_rejected(client: AsyncClient):
+    """A token signed with a different key must not be accepted."""
+    from datetime import datetime, timedelta, timezone
+
+    from jose import jwt
+
+    from app.core.config import settings
+    payload = {
+        "sub": "admin",
+        "exp": datetime.now(timezone.utc) + timedelta(minutes=5),
+    }
+    forged = jwt.encode(payload, "different-secret", algorithm=settings.algorithm)
+    res = await client.get("/api/v1/nodes", headers={"Authorization": f"Bearer {forged}"})
+    assert res.status_code == 401
+
+
+async def test_missing_authorization_header_rejected(client: AsyncClient):
+    res = await client.get("/api/v1/nodes")
+    assert res.status_code == 401
+
+
+async def test_empty_password_does_not_pass_when_hash_empty(client: AsyncClient):
+    """No credentials configured server-side must not authenticate an empty password."""
+    from app.core.config import settings
+    original_hash = settings.auth_password_hash
+    settings.auth_password_hash = ""
+    try:
+        res = await client.post("/api/v1/auth/login", json={"username": "admin", "password": ""})
+        assert res.status_code == 401
+    finally:
+        settings.auth_password_hash = original_hash
+
+
+# --- Password helper ---
+
+def test_verify_password_handles_empty_inputs():
+    """verify_password must be safe against empty plain / empty hash without raising."""
+    from app.core.security import hash_password, verify_password
+    h = hash_password("hunter2")
+    assert verify_password("hunter2", h) is True
+    assert verify_password("", h) is False
+    assert verify_password("hunter2", "") is False
+    assert verify_password("", "") is False

backend/tests/test_scan.py

@@ -37,6 +37,95 @@ async def pending_device(db_session):
     return device
 
 
+# --- _background_scan error handling ---
+
+@pytest.fixture
+async def mem_db():
+    from sqlalchemy.ext.asyncio import async_sessionmaker, create_async_engine
+
+    from app.db.database import Base
+    engine = create_async_engine("sqlite+aiosqlite:///:memory:")
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+    factory = async_sessionmaker(engine, expire_on_commit=False)
+    yield factory
+    await engine.dispose()
+
+
+@pytest.mark.asyncio
+async def test_background_scan_marks_run_failed_on_exception(mem_db):
+    """If run_scan() raises, the ScanRun must transition running → failed and the
+    session rollback path must execute without a follow-on exception."""
+    from app.api.routes.scan import _background_scan
+
+    async with mem_db() as session:
+        run = ScanRun(status="running", ranges=["10.0.0.0/24"])
+        session.add(run)
+        await session.commit()
+        run_id = run.id
+
+    with (
+        patch("app.api.routes.scan.AsyncSessionLocal", mem_db),
+        patch(
+            "app.api.routes.scan.run_scan",
+            new_callable=AsyncMock,
+            side_effect=RuntimeError("boom"),
+        ),
+    ):
+        await _background_scan(run_id, ["10.0.0.0/24"])
+
+    async with mem_db() as session:
+        refreshed = await session.get(ScanRun, run_id)
+        assert refreshed is not None
+        assert refreshed.status == "failed"
+
+
+@pytest.mark.asyncio
+async def test_background_scan_leaves_non_running_status_alone(mem_db):
+    """If the run was already stopped/cancelled before run_scan failed, _background_scan
+    must NOT overwrite that terminal status with 'failed'."""
+    from app.api.routes.scan import _background_scan
+
+    async with mem_db() as session:
+        run = ScanRun(status="cancelled", ranges=["10.0.0.0/24"])
+        session.add(run)
+        await session.commit()
+        run_id = run.id
+
+    with (
+        patch("app.api.routes.scan.AsyncSessionLocal", mem_db),
+        patch(
+            "app.api.routes.scan.run_scan",
+            new_callable=AsyncMock,
+            side_effect=RuntimeError("boom"),
+        ),
+    ):
+        await _background_scan(run_id, ["10.0.0.0/24"])
+
+    async with mem_db() as session:
+        refreshed = await session.get(ScanRun, run_id)
+        assert refreshed is not None
+        assert refreshed.status == "cancelled"
+
+
+@pytest.mark.asyncio
+async def test_background_scan_success_path_invokes_run_scan(mem_db):
+    from app.api.routes.scan import _background_scan
+
+    async with mem_db() as session:
+        run = ScanRun(status="running", ranges=["10.0.0.0/24"])
+        session.add(run)
+        await session.commit()
+        run_id = run.id
+
+    with (
+        patch("app.api.routes.scan.AsyncSessionLocal", mem_db),
+        patch("app.api.routes.scan.run_scan", new_callable=AsyncMock) as mock_run_scan,
+    ):
+        await _background_scan(run_id, ["10.0.0.0/24"])
+        mock_run_scan.assert_awaited_once()
+
+
 # --- Trigger scan ---
 
 @pytest.mark.asyncio

backend/tests/test_status_checker.py

@@ -216,6 +216,31 @@ async def test_ping_uses_windows_args_on_win32():
     assert "-c" not in captured["args"]
 
 
+# --- check_node target validation ---
+
+@pytest.mark.asyncio
+async def test_check_node_rejects_flag_like_target():
+    """A target starting with '-' must never reach subprocess invocation."""
+    from app.services.status_checker import check_node
+
+    with patch("asyncio.create_subprocess_exec") as mock_exec:
+        result = await check_node("ping", "-O", None)
+
+    mock_exec.assert_not_called()
+    assert result["status"] == "unknown"
+
+
+@pytest.mark.asyncio
+async def test_check_node_rejects_flag_like_ip():
+    from app.services.status_checker import check_node
+
+    with patch("asyncio.create_subprocess_exec") as mock_exec:
+        result = await check_node("ping", None, "-O")
+
+    mock_exec.assert_not_called()
+    assert result["status"] == "unknown"
+
+
 # --- _tcp_connect ---
 
 @pytest.mark.asyncio