fix: leftpad section codes

[KevinWu098]

Summary

1. Courses with section codes less than 5 digits long are stored in AntAlmanac as is (5001 -> 5001). The API provides them as 5 digit leftpad strings. This was resulting in us not correctly loading in courses (most critically, BIO SCI).

Above: Saved AA Data
Below: API response

Test Plan

1. Add and save courses from the 0 - 9,999 section code range
2. Loading the courses in should work as expected
3. Add and save courses from the 10,000 - 99,999 range.
4. Loading the courses should be as expected
5. Doing both together should work as expected

Issues

Closes Bug Report

[ecxyzzy]

lgtm ship boat emoji etc