Apply coredata rules: idempotent deletes and constraint checks

Delete methods no longer check RowsAffected — deletes are
idempotent. PgError handlers now check both error code and
constraint name to avoid misattributing violations. Also
migrated remaining errors.As patterns to errors.AsType.

Signed-off-by: Émile Ré <emile@probo.com>

pkg/coredata/membership_profile.go

@@ -1219,7 +1219,7 @@ VALUES (
 
 	_, err := conn.Exec(ctx, q, args)
 	if err != nil {
-		if pgErr, ok := errors.AsType[*pgconn.PgError](err); ok && pgErr.Code == "23505" {
+		if pgErr, ok := errors.AsType[*pgconn.PgError](err); ok && pgErr.Code == "23505" && pgErr.ConstraintName == "idx_profiles_identity_id_organization_id" {
 			return ErrResourceAlreadyExists
 		}
 
@@ -1409,14 +1409,10 @@ WHERE
 	args := pgx.StrictNamedArgs{"profile_id": profileID}
 	maps.Copy(args, scope.SQLArguments())
 
-	result, err := conn.Exec(ctx, q, args)
+	_, err := conn.Exec(ctx, q, args)
 	if err != nil {
 		return fmt.Errorf("cannot delete profile: %w", err)
 	}
 
-	if result.RowsAffected() == 0 {
-		return ErrResourceNotFound
-	}
-
 	return nil
 }