fix: use go-migrate pkg to init or update db schema

Instead to implement own logic how the database scheme should be updated
or migrated to a newer or older version flucky use now instead the
go-migrate package.

main.go

@@ -7,6 +7,8 @@ import (
 	"git.cryptic.systems/volker.raschek/flucky/cli"
 	"github.com/Masterminds/semver"
 
+	_ "github.com/golang-migrate/migrate/v4/database/postgres"
+	_ "github.com/golang-migrate/migrate/v4/database/sqlite3"
 	_ "github.com/lib/pq"
 	_ "github.com/mattn/go-sqlite3"
 )