fix(logs): render plain log notices verbatim instead of mangling them as timestamps

A plain message with no timestamp/level (e.g. the Windows 'Syslog is not
supported' notice) was parsed by the app-log branch, which took the first
three words as date/time/level and dropped the rest. Match the strict
'YYYY/MM/DD LEVEL - body' shape only, keep other lines whole, and drop the
leading separator when there is no stamp or level.

frontend/src/pages/index/LogModal.tsx

@@ -147,7 +147,7 @@ export default function LogModal({ open, onClose }: LogModalProps) {
               {log.levelText && <span className={`log-level ${log.levelClass}`}>{log.levelText}</span>}
               {(log.body || log.service) && (
                 <>
-                  <span> - </span>
+                  {(log.stamp || log.levelText) && <span> - </span>}
                   {log.service && <b>{log.service}</b>}
                   {log.service && log.body ? ' ' : ''}
                   <span>{log.body}</span>