feat: Intégration du backend NestJS depuis YNOV

- Framework: NestJS avec TypeORM
- Authentification: JWT (access + refresh tokens)
- Gestion utilisateurs: CRUD complet avec validation
- Routes: auth, users, parents, assistantes maternelles
- Dockerfile pour conteneurisation

backend/src/common/guards/roles.guard.ts

@@ -0,0 +1,26 @@
+import { CanActivate, ExecutionContext, Injectable } from "@nestjs/common";
+import { Reflector } from "@nestjs/core";
+import { Observable } from "rxjs";
+
+@Injectable()
+export class RolesGuard implements CanActivate {
+  constructor(private readonly reflector: Reflector) {}
+
+  canActivate(context: ExecutionContext): boolean | Promise<boolean> | Observable<boolean> {
+    const requiredRoles = this.reflector.getAllAndOverride<string[]>('roles', [
+      context.getHandler(),
+      context.getClass(),
+    ]);
+
+    if (!requiredRoles || requiredRoles.length === 0) {
+      return true;
+    }
+
+    const request = context.switchToHttp().getRequest();
+    const user = request.user;
+    if (!user || !user.role) {
+      return false;
+    }
+    return requiredRoles.includes(user.role);
+  }
+}