fix in-app question upload sharing stale parser, hide weak-area toggle after generation, retry passage question shortfalls

keep passage questions grouped, gate practice quizzes behind student login, fix sheet parsing, drop category accuracy feature

support header-labeled sheet columns in question bank seeding

remove quiz delete-all, restore question-bank wipe-all, skip llm category when sheet already has it

quiz/bank wipe option, LLM answer check

minor UI fixes (solid navy header)