fix(syslog): a row from before the name split, last seen as a device, stays that device's (#6096)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/integration/test_syslog.py

@@ -99,6 +99,20 @@ def test_devices_through_dockers_address_are_told_apart_by_name(app, monkeypatch
             got = sorted((r.address, r.sender, r.lines_total, r.last_line) for r in rows)
             assert got == [("10.0.0.2", "AsusNAS", 2, "d"), ("10.0.0.2", "SynNAS", 2, "c"),
                            ("10.9.0.1", "", 1, "e")]
+            await s.execute(delete(SyslogSource))
+            await s.commit()
+        # A row from before the split, last seen under a device's name, is that device's.
+        async with app.db_sessionmaker() as s:
+            async with s.begin():
+                s.add(SyslogSource(address="10.0.0.3", state="accepted", name="DS923", hostname_seen="DS923",
+                                   first_seen_at=now, last_seen_at=now, lines_total=3))
+        async with app.db_sessionmaker() as s:
+            async with s.begin():
+                await receiver.store_lines(s, [line("10.0.0.3", "DS923", "f"), line("10.0.0.3", "util", "g")])
+        async with app.db_sessionmaker() as s:
+            rows = (await s.execute(select(SyslogSource))).scalars().all()
+            got = sorted((r.sender, r.state, r.name, r.lines_total) for r in rows)
+            assert got == [("DS923", "accepted", "DS923", 4), ("util", "offered", "", 1)]
         async with app.db_sessionmaker() as s:
             async with s.begin():
                 await s.execute(delete(SyslogSource))