fix: Prevent DatePicker time input from resetting date to today

[Lucaka]

PR Description

Problem Encountered:

When assigning a specific date (e.g., value = new Date('2025-02-14')), manually entering a value in a type="time" <DatePicker> component causes the date to reset to today's date.

Reproduction Example:

<DatePicker v-model:value="value" type="date"></DatePicker> 
<DatePicker v-model:value="value" type="time" format="HH:mm"></DatePicker>

• Expected: The time input should update only the time while preserving the original date (2025-02-14).
• Actual: The date is reset to today (new Date()).

Solution in This PR:

• In PickerInput, when handleChange is triggered, we retain the original date while updating only the time.
• Instead of using parseDate, which resets the date to today, we ensure that only the time portion is modified.
• This prevents unexpected date resets and ensures consistent behavior across type="time" inputs.