Project preference list not considered until full

[lonnychen]

Running the new algorithm through test_algorithm.py after updating at this commit, the below issue was found.

Issue: Project preference list not considered until full

• test_td_1 output: Checking for stable match: s2 and p1 -> INVALID: s2 is not in p1 preference list!
• Flask app: see screenshot below (confirms test_td_1 output)
• Possible Fix: only assign a student to a project if they are in that project's preference list (at all times, not just when project is full)

Originally posted by @lonnychen in https://github.com/data-structures-algorithms-group4/student-project-matching/issues/11#issuecomment-2036632479

[lonnychen]

This issue can be closed as the new algorithm committed here now considers the project preference list before matching.