Fix ensureBootstrapAdmin: cast $1 to uuid and target_id to text

The audit_events insert in the bootstrap path was reusing $1 for
both user_id (uuid) and target_id (text), which Postgres rejected
with "inconsistent types deduced for parameter $1". The whole
transaction rolled back, so the bootstrap user never got created
on fresh installs and the operator hit "Invalid email or password"
on first sign-in with no other diagnostic.

Use two separate parameters with explicit casts. The metadata cast
to jsonb stays.