Implement Validations for Time Input, Overlapping Events, and Prevent Past Date Event Creation

[Brijitha1609]

Is this task related to a feature or a bug? Please include relevant issue numbers below. Given the current implementation of the "Request for Help" page, When the user interacts with the calendar to select dates and times, Then the time input allows submitting the form without providing a start and end time, the calendar permits overlapping events which might cause confusion, and it’s possible to create events for past dates, which ideally should be restricted to future dates for better planning.

Describe the solution you'd like The following improvements should be made:

• Add validation to ensure that the form cannot be submitted when both the start and end times are left blank.
• Implement functionality to prevent overlapping events, ensuring that volunteers or events do not overlap in time slots.
• Restrict the creation of events for past dates and allow scheduling only for present or future dates.

Acceptance Criteria:

• [x] Validate time input to ensure that the form cannot be submitted when both the start and end times are left blank.
• [x] Prevent the creation of overlapping events.
• [x] Restrict event creation to future dates only.