Fix semester context, attendance rosters, and billing workflows

- load global semester helpers consistently and use date-based semester defaults
- fix grading and daily attendance duplicate student/section rows
- keep attendance violations scoped to the current semester by default
- update invoice, refund, discount, payment, and financial aid flows
- add configuration cleanup migrations for duplicate calendar/semester keys
- refresh parent registration/report-card and print request handling
- update related models, services, views, cron notes, and test coverage

app/Views/discounts/apply_voucher.php

@@ -5,7 +5,7 @@
     <h1>Apply Discount Voucher</h1>
     <?= $this->include('partials/academic_filter') ?>
 
-    <form method="post" action="">
+    <form method="post" action="<?= site_url('discount/apply') ?>">
         <?= csrf_field() ?>
         <div class="d-flex gap-2 mb-3 justify-content-end">
             <div>