feat: implement Redis session management and user authentication flow

app/gateway-api/src/auth/userRepository.ts

@@ -0,0 +1,34 @@
+export interface UserRecord {
+    id: string;
+    username: string;
+    displayName: string;
+    passwordHash: string;
+    passwordSalt: string;
+    createdAt: string;
+}
+
+export interface PublicUser {
+    id: string;
+    username: string;
+    displayName: string;
+    createdAt: string;
+}
+
+export const toPublicUser = (user: UserRecord): PublicUser => ({
+    id: user.id,
+    username: user.username,
+    displayName: user.displayName,
+    createdAt: user.createdAt,
+});
+
+export interface CreateUserInput {
+    username: string;
+    password: string;
+    displayName?: string;
+}
+
+export interface UserRepository {
+    findByUsername(username: string): Promise<UserRecord | null>;
+    createUser(input: CreateUserInput): Promise<UserRecord>;
+    verifyPassword(user: UserRecord, password: string): Promise<boolean>;
+}