refactor(data): add mock API adapters, id utility, and toast feedback

lib/api/users.ts

@@ -0,0 +1,13 @@
+import { currentUser, mockUsers } from "@/lib/mock"
+
+export function listUsers() {
+  return mockUsers
+}
+
+export function getUserById(userId: string) {
+  return mockUsers.find((user) => user.id === userId)
+}
+
+export function getCurrentUserForLogin() {
+  return currentUser
+}