fix: custom-cron-ui (#15786)

Fixes #14723 

### Summary
Fixes a UI while creating a custom CRON

### Changes Made
- updated `WorkflowEditTriggerCronForm.tsx` to use the predefined
`FormSelectFieldInput.tsx` instead of using `Select.tsx`
- added `hint` prop to `FormSelectFieldInput.tsx`
- updated styling for showing `Upcoming execution time`
- added conditional render for `Schedule` and `Upcoming Execution Time` 
- `Schedule`  section is not rendered in Custom Cron

### Steps to Reproduce (Before Fix)
1. Navigate to - /object/workflow/xxxx
2. Try adding a new Trigger
3. Set Trigger Interval to Cron (Custom)


### Before 

![Screenshot 2025-11-13 at 4 00
29 PM](https://github.com/user-attachments/assets/f85ab0fa-cb71-4257-9659-10e1404f17ed)


### After

![Screenshot 2025-11-13 at 4 00
55 PM](https://github.com/user-attachments/assets/db1d54ef-e5d5-42e2-9de5-c1f91f46088e)

---------

Co-authored-by: Charles Bochet <charles@twenty.com>

packages/twenty-front/src/modules/object-record/record-field/ui/form-types/components/FormSelectFieldInput.tsx

@@ -3,6 +3,7 @@ import { FormFieldInputInnerContainer } from '@/object-record/record-field/ui/fo
 import { FormFieldInputRowContainer } from '@/object-record/record-field/ui/form-types/components/FormFieldInputRowContainer';
 import { VariableChipStandalone } from '@/object-record/record-field/ui/form-types/components/VariableChipStandalone';
 import { type VariablePickerComponent } from '@/object-record/record-field/ui/form-types/types/VariablePickerComponent';
+import { InputHint } from '@/ui/input/components/InputHint';
 import { InputLabel } from '@/ui/input/components/InputLabel';
 import { Select } from '@/ui/input/components/Select';
 import { GenericDropdownContentWidth } from '@/ui/layout/dropdown/constants/GenericDropdownContentWidth';
@@ -18,6 +19,7 @@ import { type SelectOption } from 'twenty-ui/input';
 
 type FormSelectFieldInputProps = {
   label?: string;
+  hint?: string;
   defaultValue: string | undefined;
   onChange: (value: string | null) => void;
   VariablePicker?: VariablePickerComponent;
@@ -27,6 +29,7 @@ type FormSelectFieldInputProps = {
 
 export const FormSelectFieldInput = ({
   label,
+  hint,
   defaultValue,
   onChange,
   VariablePicker,
@@ -162,6 +165,7 @@ export const FormSelectFieldInput = ({
           />
         )}
       </FormFieldInputRowContainer>
+      {hint && <InputHint>{hint}</InputHint>}
     </FormFieldInputContainer>
   );
 };