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/Controllers/View/CertificateController.php

@@ -37,6 +37,7 @@ class CertificateController extends BaseController
             ->join('classSection cs', 'cs.class_section_id = sc.class_section_id')
             ->where('s.is_active', 1)
             ->where('sc.school_year', $schoolYear)
+            ->groupBy('s.id, s.firstname, s.lastname, sc.class_section_id, cs.class_section_name')
             ->orderBy('s.firstname', 'ASC')
             ->orderBy('s.lastname', 'ASC')
             ->get()
@@ -105,10 +106,18 @@ class CertificateController extends BaseController
         // ── Build per-class buckets and stats ──────────────────────────────────
         $studentsByClass = [];
         $statsPerClass   = [];
+        $seenEnrollments = [];
 
         foreach ($allEnrolled as $row) {
             $sid  = (int)$row['student_id'];
             $csid = (int)$row['class_section_id'];
+            $enrollmentKey = $csid . ':' . $sid;
+
+            if (isset($seenEnrollments[$enrollmentKey])) {
+                continue;
+            }
+
+            $seenEnrollments[$enrollmentKey] = true;
 
             if (!isset($statsPerClass[$csid])) {
                 $statsPerClass[$csid] = [
@@ -293,7 +302,7 @@ class CertificateController extends BaseController
                 ->with('error', 'Please select at least one student.');
         }
 
-        $studentIds = array_filter(array_map('intval', $studentIds));
+        $studentIds = array_values(array_unique(array_filter(array_map('intval', $studentIds))));
         $certDate   = preg_replace('/[^0-9\/\-]/', '', $certDate);
 
         if (empty($studentIds)) {
@@ -661,4 +670,4 @@ class CertificateController extends BaseController
         $pdf->SetTextColor(0, 0, 0);
         $pdf->Text($x, $y, $text);
     }
-}
+}