test: split monolithic test_scan into a scan/ subpackage

Break the 1897-line test_scan.py into topic modules under tests/scan/
(routes, approve, properties, run) sharing fixtures via a package
conftest.py and pure builders via helpers.py. Same 80 tests, no
behavior change; full suite 627 passed.

ha-relevant: no

backend/tests/scan/conftest.py

@@ -0,0 +1,84 @@
+"""Fixtures shared across the scan test modules."""
+import uuid
+
+import pytest
+
+from app.db.models import PendingDevice
+
+
+@pytest.fixture
+async def pending_device(db_session):
+    import uuid
+    device = PendingDevice(
+        id=str(uuid.uuid4()),
+        ip="192.168.1.100",
+        mac="aa:bb:cc:dd:ee:ff",
+        hostname="my-server",
+        os="Linux",
+        services=[{"port": 22, "name": "ssh"}],
+        suggested_type="server",
+        status="pending",
+    )
+    db_session.add(device)
+    await db_session.commit()
+    await db_session.refresh(device)
+    return device
+
+
+@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.fixture
+async def two_pending_devices(db_session):
+    devices = []
+    for i in range(2):
+        d = PendingDevice(
+            id=str(uuid.uuid4()),
+            ip=f"192.168.1.{10 + i}",
+            mac=None,
+            hostname=f"host-{i}",
+            os=None,
+            services=[],
+            suggested_type="generic",
+            status="pending",
+        )
+        db_session.add(d)
+        devices.append(d)
+    await db_session.commit()
+    for d in devices:
+        await db_session.refresh(d)
+    return devices
+
+
+@pytest.fixture
+async def zigbee_pending_device(db_session):
+    device = PendingDevice(
+        id=str(uuid.uuid4()),
+        ip=None,
+        mac=None,
+        hostname=None,
+        friendly_name="bulb_1",
+        services=[],
+        suggested_type="zigbee_enddevice",
+        device_subtype="EndDevice",
+        ieee_address="0xABCDEF",
+        vendor="IKEA",
+        model="TRADFRI",
+        lqi=180,
+        status="pending",
+        discovery_source="zigbee",
+    )
+    db_session.add(device)
+    await db_session.commit()
+    await db_session.refresh(device)
+    return device