feat: enhance assignments module with user role handling and upload file type definition

feat(backend): add student payment APIs and stabilize transcript/assignment responses.

feat: implement core backend modules, notification system, and AI agent skill documentation

fix(assignments): change delete instruction endpoint to accept driveId instead of DB PK

feat(assignments): add endpoint to delete assignment instruction files

feat(drive-integration): refactor Google Drive integration with folder service and DB schema improvements

Labs - Quizzes - Assignment student Dashboard still under work

try after off

Clean initial commit without secrets