error message in generate student report, gate quiz records on final save, randomize question bank, UI changes

fix student records, dashboard illustration changed, report generation fixed, and UI changes

question generation feature, date selection, changes to UI login page and icons

Refactor to add answer grid & assoicate llm parsing

Simplify: send raw data to LLM, let user's prompt control interpretation

Add final prompt preview tab with real student data substitution

Add prompt editor and data preview back to Step 2

Add data preview modal before report generation

Redesign ClassLens v2: 3-step exam analysis workflow