Try to search in path instead of using a hardcoded default path for pg_dump (and restore)

Hi there,

I came across the issue that when I try to run pg_dump from the UI the path for the executable has a hard-coded default.
While on the most distributions this might not be an issue but as I use nixos the location of the executable is different.

My suggestion would be to search for the executable in the path env by default and then fallback to a (maybe hard-coded) default executable path.