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

frontend/src/services/level-mapping.service.ts

@@ -0,0 +1,13 @@
+import { api } from "@/lib/api-client";
+import type { LevelMapping, LevelMappingRow } from "@/types";
+import type { ApiSuccessResponse } from "@/types";
+
+export const levelMappingService = {
+  get: (entityId: number) => api.get<LevelMapping>(`/entity/${entityId}/level-mapping`),
+
+  update: (entityId: number, mappings: LevelMappingRow[]) =>
+    api.put<ApiSuccessResponse>(`/entity/${entityId}/level-mapping`, { mappings }),
+
+  resetToDefault: (entityId: number) =>
+    api.post<ApiSuccessResponse>(`/entity/${entityId}/level-mapping/reset`),
+};