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/StudentModel.php

@@ -150,17 +150,14 @@ class StudentModel extends Model
      */
     public function getStudentsWithAssignments()
     {
-        // Retrieve school year and semester from the configuration table
+        // Retrieve school year from configuration and derive the current semester from calendar dates.
         $configTable = $this->db->table('configuration');
         $schoolYear = $configTable->select('config_value')
             ->where('config_key', 'school_year')
             ->get()
             ->getRowArray()['config_value'];
 
-        $semester = $configTable->select('config_value')
-            ->where('config_key', 'semester')
-            ->get()
-            ->getRowArray()['config_value'];
+        $semester = getSemester();
 
         return $this->db->table('students')
             ->select('