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>

plugins/syslog/receiver.py

@@ -249,6 +249,15 @@ async def store_lines(session, lines: list[Received]) -> None:
     sources = {(s.address, s.sender): s for s in (await session.execute(
         select(SyslogSource).where(SyslogSource.address.in_(addresses)))).scalars()}
     new = [k for k in by_sender if k not in sources]
+    for key in [k for k in new if k[1]]:
+        # A row from before devices at Docker's address were told apart by
+        # name, last seen under this one, is this device: it keeps its state
+        # and name rather than a new row being offered beside it.
+        before = sources.get((key[0], ""))
+        if before is not None and before.hostname_seen == key[1]:
+            before.sender = key[1]
+            sources[key] = sources.pop((key[0], ""))
+            new.remove(key)
     if new:
         known = (await session.execute(select(func.count()).select_from(SyslogSource))).scalar_one()
         for key in new: