feat(v3): restructure project + add complete frontend

- Restructure: move backend from new_project/ to backend/
- Add full React/TypeScript frontend (37 pages, 17 services, 16 type defs, 11 query hooks)
- Add docs/ with SRS specs, user stories, and workflow documentation
- Update .gitignore for new directory layout

Workflows implemented:
  WF1 User Signup, WF2 Placement Test, WF3 Exam Configuration,
  WF4 General English Exam, WF5 Course Generation,
  WF6 Entity Student Onboarding, AI Course Generation,
  Adaptive Learning Engine UI, White-Label Branding, Score Release

Made-with: Cursor

src/components/ui/collapsible.tsx

@@ -0,0 +1,9 @@
+import * as CollapsiblePrimitive from "@radix-ui/react-collapsible";
+
+const Collapsible = CollapsiblePrimitive.Root;
+
+const CollapsibleTrigger = CollapsiblePrimitive.CollapsibleTrigger;
+
+const CollapsibleContent = CollapsiblePrimitive.CollapsibleContent;
+
+export { Collapsible, CollapsibleTrigger, CollapsibleContent };