web: Show host name in live-stats error messages (#170)

Error rows now include the host name (e.g., "nuc: Connection refused")
and have proper id/data-host attributes so they get replaced in place
instead of accumulating on each refresh interval.

src/compose_farm/web/routes/containers.py

@@ -268,7 +268,8 @@ async def get_containers_rows_by_host(host_name: str) -> HTMLResponse:
             error,
         )
         return HTMLResponse(
-            f'<tr class="text-error"><td colspan="12" class="text-center py-2">Error: {error}</td></tr>'
+            f'<tr id="error-{host_name}" class="text-error" data-host="{host_name}">'
+            f'<td colspan="12" class="text-center py-2">{host_name}: {error}</td></tr>'
         )
 
     if not containers: