fix: few UI/usability issues with the time input field

frontend/app_flowy/lib/plugins/grid/application/cell/date_cal_bloc.dart

@@ -108,7 +108,7 @@ class DateCalBloc extends Bloc<DateCalEvent, DateCalState> {
         (err) {
           switch (ErrorCode.valueOf(err.code)!) {
             case ErrorCode.InvalidDateTimeFormat:
-              updateCalData(none(), Some(timeFormatPrompt(err)));
+              updateCalData(state.calData, Some(timeFormatPrompt(err)));
               break;
             default:
               Log.error(err);

frontend/app_flowy/lib/plugins/grid/presentation/widgets/cell/date_cell/date_editor.dart

@@ -261,6 +261,7 @@ class _TimeTextFieldState extends State<_TimeTextField> {
             child: RoundedInputField(
               height: 40,
               focusNode: _focusNode,
+              autoFocus: true,
               hintText: state.timeHintText,
               controller: _controller,
               style: const TextStyle(fontSize: 14, fontWeight: FontWeight.w500),

frontend/rust-lib/flowy-grid/src/services/field/type_options/date_type_option/date_type_option.rs

@@ -52,7 +52,7 @@ impl DateTypeOptionPB {
 
         let mut time = "".to_string();
         if has_time && self.include_time {
-            let fmt = format!("{} {}", self.date_format.format_str(), self.time_format.format_str());
+            let fmt = format!("{}{}", self.date_format.format_str(), self.time_format.format_str());
             time = format!("{}", utc.format_with_items(StrftimeItems::new(&fmt))).replace(&date, "");
         }