Branch fix mobile frontend

[zachchong]

Fix 1: Mobile: Fix the text overflow issue on calendar (days)
Before:

After:

Fix 2: As a mobile user, I want to select dates easily by tapping anywhere on the date cell, so that I don’t have to press exactly on the number for it to respond.

[Copilot]

Pull request overview

This PR addresses two mobile usability issues in the booking calendar component: text overflow in calendar day headers and improved date cell clickability.

• Changed day header format from "EEEE" (full day name) to "EEE" (abbreviated) to prevent text overflow
• Added selectable={true} property and styling changes to make entire date cells clickable instead of just the date numbers

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
frontend/src/utils/calendar-utils.ts	Updated date format constants to use abbreviated day names
frontend/src/components/booking-calendar/booking-calendar.tsx	Added selectable prop and weekday format configuration
frontend/src/components/booking-calendar/booking-calendar.module.scss	Added global styles to expand clickable area of date cells

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[Copilot]

[nitpick] The constant name WEEKDAY_FORMAT is ambiguous because both DAY_HEADER_FORMAT and WEEKDAY_FORMAT use the same format value 'EEE'. Consider renaming to WEEKDAY_COLUMN_FORMAT or WEEK_VIEW_DAY_FORMAT to clarify that this is specifically for the weekday column headers in month view, distinct from the day header used elsewhere.

Suggested change

	export const WEEKDAY_FORMAT = "EEE";
	export const WEEKDAY_COLUMN_FORMAT = "EEE";