fix: resolve TypeError in grades PDF generation

Resolves a `TypeError: '<=' not supported between instances of 'int' and 'str'` that occurred during grades PDF generation.
The `bimester` field in the `Grade` model is a `CharField` (e.g., '1B', '2B'), but it was being compared directly with integers in `api/students/views.py`.
The fix involves extracting the numeric part of the `bimester` string (e.g., '1B' -> 1) before using it in comparisons and as an index.

Author: Pinheiro-Reis

api/students/views.py

@@ -86,8 +86,9 @@ def download_grades_pdf(self, request, pk=None):
             # Initialize with None for each bimester
             bimester_grades = [None, None, None, None]
             for grade in all_grades.filter(subject__full_name=subject):
-                if 1 <= grade.bimester <= 4:
-                    bimester_grades[grade.bimester - 1] = grade.value
+                bimester_num = int(grade.bimester[0])  # Extract the numeric part (e.g., "1B" -> 1)
+                if 1 <= bimester_num <= 4:
+                    bimester_grades[bimester_num - 1] = grade.value
             data[subject] = bimester_grades
         return pdfgen(
             "grades.html",