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/Models/StudentClassModel.php

@@ -157,11 +157,22 @@ class StudentClassModel extends Model
             );
         }
 
-        return $builder
+        $rows = $builder
             ->orderBy('students.lastname', 'ASC')
             ->orderBy('students.firstname', 'ASC')
             ->get()
             ->getResultArray();
+
+        $unique = [];
+        foreach ($rows as $row) {
+            $studentId = (int) ($row['student_id'] ?? 0);
+            if ($studentId <= 0 || isset($unique[$studentId])) {
+                continue;
+            }
+            $unique[$studentId] = $row;
+        }
+
+        return array_values($unique);
     }
 
     /**
@@ -530,4 +541,4 @@ class StudentClassModel extends Model
 
         return $counts;
     }
-}
+}