feat: set new default log retention policy of 90 days

files/etc/logrotate.conf

 # see "man logrotate" for details
 # rotate log files weekly
-weekly
+daily
 
-# keep 13 weeks (so 1/4 of a year) worth of backlogs
-rotate 13
+# keep 90 days worth of backlogs as required by SLUBs retention policy and backed by SächsISichG §13
+rotate 90
 
 # create new (empty) log files after rotating old ones
 create