Add Guest Count with Dynamic Price Calculation

[AMANkumar0004]

Feature Overview:
Currently listing price is fixed. We need to allow users to select number of guests and dynamically adjust price.

Requirements:
Add guest count input in booking form
Add maxGuests field in Listing schema
Add guests field in Booking schema
Calculate total price using formula: basePrice multiplied by numberOfGuests multiplied by numberOfNights
Prevent booking if guest count exceeds maxGuests

Technical Notes:
Update Listing model
Update Booking model
Add validation in controller
Optionally add live price preview using JavaScript

Acceptance Criteria:
Price calculation works correctly
Guest limit validation works
Proper error messages displayed

[Sappymukherjee214]

@AMANkumar0004 I would like to work on this issue, please assign it to me.