[hotfix] add make command to fix corrupted postgres write-ahead log

context:

• twice in the last year, we have seen signalboost get in a broken state after a database backup job in which it cannot restart because it fails to connect to postgres, which itself cannot start because of a corrupted write-ahead log
• we would like to be able to fix this problem as quickly as possible if it arises again without having to think about things or look them up while we are stressed out

changes:

• this MR provides a one-line make command to repair the write-ahead-log and is a down payment on eventually automating the fix