onConflictDoNothing is only defined on Drizzle's SQLite and Postgres
insert builders. MySQL insert builder lacks this method, causing a
TypeError at startup for all MySQL/MariaDB installations.
Replaced with a dialect-neutral pre-filter that queries existing widget
IDs and only inserts rows that don't already exist. This matches the
count-first/skip pattern used by every other seed function in the file
and keeps a single code path across all dialects.
Closes#5967
ajnart
1463dde802