feat: Implement Booking Confirmation UI

[SujalTripathi]

Description

The homepage has "Browse classes" and "Book a Session" CTAs but no
actual booking form exists. The /api/bookings route exists but has
no frontend to connect to it.

Current Behavior

• No booking form or modal exists
• "Book a Session" button has no functionality
• /api/bookings POST endpoint is unused from the frontend

Expected Behavior

• Clicking "Book a Session" opens a booking modal/form
• Form fields: learner name, email, preferred date, preferred time,
  session type (1:1 or group), message to instructor
• On submit: calls POST /api/bookings and shows success confirmation
• Success state shows booking summary with instructor name and time

Tech Involved

• React useState for modal and form state
• fetch to call POST /api/bookings
• Tailwind CSS modal/form components
• Form validation

Acceptance Criteria

• Booking modal/form component created
• All required fields with validation
• Connects to POST /api/bookings
• Success confirmation message shown
• Error state handled gracefully
• Mobile responsive form

Contributing on behalf of NSoC'26 | @Mehren7 please assign me

[SujalTripathi]

@Mehren7 please add label also and its my request to add as level3 bcz i am just making booking modal, form field, summary ...