improvement: some files replaced, lots of them i shall say. AGENT.MD file created. some rules and skills added for cursor agent.

.cursor/rules/backend-nestjs.mdc

@@ -0,0 +1,41 @@
+---
+description: Backend NestJS modules, Prisma, permissions, guards
+globs: backend/src/**
+alwaysApply: false
+---
+
+# Backend conventions
+
+## Module layout
+
+`backend/src/modules/{feature}/` → `{feature}.module.ts`, `.controller.ts`, `.service.ts`, `dto/`.
+
+Register new modules in `app.module.ts`.
+
+## Errors
+
+Use coded errors — not raw user-facing strings:
+
+```typescript
+throw new AppException(ErrorCode.PERMISSION_DENIED, HttpStatus.FORBIDDEN);
+```
+
+- Codes: `backend/src/common/errors/error-codes.ts`
+- DTO validation: `{ message: ErrorCode.VALIDATION_* }` on class-validator decorators
+- Global filter: `HttpExceptionFilter` in `main.ts`
+
+## Permissions
+
+- Check access with `hasEffectivePermission(membership, 'TAB_*')` from `common/membership-permissions.ts`.
+- Clinic-only routes: `ClinicOrgGuard`. Lab-only: `LabOrgGuard`.
+- Feature-specific checks belong in the **service**, not only the controller.
+
+## Prisma
+
+- Schema: `backend/prisma/schema.prisma`
+- Always add a migration for schema changes (`npm run prisma:migrate` in backend).
+- Seed permissions stay in sync with `ALL_TAB_PERMISSIONS` in `common/permissions.ts`.
+
+## API responses
+
+Prefer `{ success: true, data: ... }` shape consistent with existing modules.