Use custom ports for postgres/hydra

Use custom ports so hydra and postgres can run in environments where
the default ports are in use already.

flake.nix

@@ -300,7 +300,7 @@
           export HYDRA_HOME="src/"
           mkdir -p .hydra-data
           export HYDRA_DATA="$(pwd)/.hydra-data"
-          export HYDRA_DBI='dbi:Pg:dbname=hydra;host=localhost;'
+          export HYDRA_DBI='dbi:Pg:dbname=hydra;host=localhost;port=64444'
         '';
       });