Change deposit to $45, add balance-due-at-pickup calculations

- DEPOSIT_AMOUNT changed from $100 to $45
- Balance (package price minus $45) shown dynamically in booking form when package selected
- Customer confirmation email shows breakdown: deposit hold + balance at pickup
- Admin email table includes deposit hold and balance columns
- Admin booking flow step 5 shows deposit held + balance at pickup
- Reminder email deposit detail updated to reflect held deposit and balance
- Live status field shows $45 during card authorization flow

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

db.php

@@ -17,7 +17,7 @@ define('SQUARE_ACCESS_TOKEN', 'EAAAl3FsAu_2ri8kZE_ENEyi2T_C8HXXm5XQFY6Lbnd8SX6Fq
 define('SQUARE_APP_ID',       'sq0idp-YSM7BU9IVyOWSzpeP-0nzQ');
 define('SQUARE_LOCATION_ID',  'L8GZYHYKE95CE');
 define('SQUARE_VERSION',      '2024-01-18');
-define('DEPOSIT_AMOUNT',       100.00); // $100 refundable security deposit hold
+define('DEPOSIT_AMOUNT',        45.00); // $45 deposit hold — balance due at pickup
 
 define('PACKAGES', [
     'half-day' => ['label' => 'Half Day (4 hrs)',    'amount' => 99.00,  'days' => 0],