fix(crud): skip generated and read-only columns on insert and update

Read-merge-update wrote every model column back, so GENERATED ALWAYS
columns failed with SQLSTATE 428C9. Add a bun 'generated' tag option,
reflection.NonWritableColumns/RemoveNonWritableColumns, and apply them
in resolvespec, restheadspec, websocketspec, mqttspec, resolvemcp and
the nested CUD processor. Add ExcludeColumn to InsertQuery/UpdateQuery
for model-based writes.

pkg/resolvemcp/handler.go

@@ -559,6 +559,7 @@ func (h *Handler) executeCreate(ctx context.Context, schema, entity string, data
 			if len(cols) == 0 {
 				return invalidArg("no writable fields in data")
 			}
+			reflection.RemoveNonWritableColumns(model, cols)
 			q := tx.NewInsert().Table(tableName)
 			for key, value := range cols {
 				q = q.Value(key, value)
@@ -726,6 +727,7 @@ func (h *Handler) executeUpdate(ctx context.Context, schema, entity, id string,
 			existingMap[key] = v
 		}
 
+		reflection.RemoveNonWritableColumns(model, setCols)
 		q := tx.NewUpdate().Table(tableName).SetMap(setCols).
 			Where(fmt.Sprintf("%s = ?", common.QuoteIdent(pkName)), id)
 		res, err := q.Exec(ctx)

pkg/resolvemcp/writewhere.go

@@ -194,6 +194,7 @@ func (h *Handler) executeWhere(ctx context.Context, req whereRequest) (_ *whereR
 		cond := fmt.Sprintf("%s IN (%s)", common.QuoteIdent(pkName), strings.Join(inList, ", "))
 		var affected int64
 		if req.op == "update" {
+			reflection.RemoveNonWritableColumns(model, setCols)
 			r, err := tx.NewUpdate().Table(tableName).SetMap(setCols).Where(cond, ids...).Exec(ctx)
 			if err != nil {
 				return fmt.Errorf("error updating records: %w", err)