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/websocketspec/handler_test.go

@@ -226,6 +226,11 @@ func (m *MockInsertQuery) OnConflict(action string) common.InsertQuery {
 	return args.Get(0).(common.InsertQuery)
 }
 
+func (m *MockInsertQuery) ExcludeColumn(columns ...string) common.InsertQuery {
+	args := m.Called(columns)
+	return args.Get(0).(common.InsertQuery)
+}
+
 func (m *MockInsertQuery) Returning(columns ...string) common.InsertQuery {
 	args := m.Called(columns)
 	return args.Get(0).(common.InsertQuery)
@@ -254,6 +259,11 @@ func (m *MockUpdateQuery) Model(model interface{}) common.UpdateQuery {
 	return args.Get(0).(common.UpdateQuery)
 }
 
+func (m *MockUpdateQuery) ExcludeColumn(columns ...string) common.UpdateQuery {
+	args := m.Called(columns)
+	return args.Get(0).(common.UpdateQuery)
+}
+
 func (m *MockUpdateQuery) Table(table string) common.UpdateQuery {
 	args := m.Called(table)
 	return args.Get(0).(common.UpdateQuery)