feat(omnichannel): Add time validation for Business Hours form

Description

Currently, the Business Hours form (BusinessHoursForm.tsx) allows users to set invalid time configurations:

1. Start time equal to finish time (e.g., Open: 09:00, Close: 09:00)
2. Start time greater than finish time (e.g., Open: 18:00, Close: 08:00)

These invalid configurations can cause unexpected behavior in the livechat business hours logic.

Current Behavior

• No validation on start/finish time inputs
• Invalid time configurations are saved to the database
• TODO comments already exist in the codebase (lines 37-38 of BusinessHoursForm.tsx)

Expected Behavior

• Show error message when start time equals finish time
• Show error message when start time is greater than finish time
• Prevent form submission until times are valid

Screenshots/Evidence

The TODO comments in the codebase:

// TODO: add time validation for start and finish not be equal on UI
// TODO: add time validation for start not be higher than finish on UI

Start with BusinessHoursForm.tsx and inspect the time inputs, form submission flow, and the TODO comments around lines 37-38. Confirm how the form currently saves values, then make the completed behavior show errors for equal or reversed times and prevent submission until the times are valid.