[Maintenance] - Marking Future Availability Fix

[cielbellerose]

Description

On the edit availability modal, marking available hours for future weeks is difficult because every time a click is registered the weeks jump back to the current week. This only allows for maybe one or two hours at a time to be highlighted for future weeks which is frustrating

Acceptance Criteria

• Marking availability on future weeks should work identically to marking the current week

Proposed Solution

in SettingsPage/UserScheduleSettings/Availability/EditAvailability.tsx
toggleTimeSlot recomputes the displayed week using initialDate, which snaps back to the current week when changes are made. we want toggleTimeSlot to recompute using the currently displayed date instead

• add a new use state to track displayed date instead of always using initial date

Mocks