Add ciclo de vida de sesión y helpers de usuario actual

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

mvp/b2c/src/lib/auth/current-user.ts

@@ -0,0 +1,25 @@
+import { redirect } from 'next/navigation';
+import { getSessionUser } from './session';
+import { resolveTenantId, type AuthUser } from './authz';
+
+export async function getCurrentUser(): Promise<AuthUser | null> {
+  return getSessionUser();
+}
+
+export async function requireUser(): Promise<AuthUser> {
+  const user = await getSessionUser();
+  if (!user) redirect('/login');
+  return user;
+}
+
+export async function requireAdmin(): Promise<AuthUser> {
+  const user = await getSessionUser();
+  if (!user) redirect('/login');
+  if (user.role !== 'admin') redirect('/panel');
+  return user;
+}
+
+export async function getCurrentTenantId(): Promise<string> {
+  const user = await getSessionUser();
+  return resolveTenantId(user);
+}