feat: implement user authentication with login and register

- Add login screen with email/username support
- Add register screen with email validation
- Implement AuthStore with expo-secure-store (native) / localStorage (web)
- Add X-User-Id header authentication (simple auth without JWT)
- Rename displayName to userName across codebase
- Add findByUserName() to UserRepository
- Check for existing email AND username on registration
- Add AuthButton component with shadow effect
- Add logout button to Header
- Add hash-password.js utility script for manual password resets
- Update CORS to allow X-User-Id header

apps/server/src/repositories/mongo/MongoUserRepository.ts

@@ -1,23 +1,38 @@
 import { User } from "@caldav/shared";
 import { UserRepository, CreateUserData } from "../../services/interfaces";
 import { Logged } from "../../logging";
-import { UserModel } from "./models";
+import { UserModel, UserDocument } from "./models";
+
+function toUser(doc: UserDocument): User {
+  return {
+    id: doc._id.toString(),
+    email: doc.email,
+    userName: doc.userName,
+    passwordHash: doc.passwordHash,
+    createdAt: doc.createdAt,
+    updatedAt: doc.updatedAt,
+  };
+}
 
 @Logged("MongoUserRepository")
 export class MongoUserRepository implements UserRepository {
   async findById(id: string): Promise<User | null> {
-    throw new Error("Not implemented");
+    const user = await UserModel.findById(id);
+    return user ? toUser(user) : null;
   }
 
   async findByEmail(email: string): Promise<User | null> {
     const user = await UserModel.findOne({ email: email.toLowerCase() });
-    // NOTE: Casting required because Mongoose's toJSON() type doesn't reflect our virtual 'id' field
-    return (user?.toJSON() as unknown as User) ?? null;
+    return user ? toUser(user) : null;
+  }
+
+  async findByUserName(userName: string): Promise<User | null> {
+    const user = await UserModel.findOne({ userName });
+    return user ? toUser(user) : null;
   }
 
   async create(data: CreateUserData): Promise<User> {
     const user = await UserModel.create(data);
-    // NOTE: Casting required because Mongoose's toJSON() type doesn't reflect our virtual 'id' field
-    return user.toJSON() as unknown as User;
+    return toUser(user);
   }
 }

apps/server/src/repositories/mongo/models/UserModel.ts

@@ -21,7 +21,7 @@ const UserSchema = new Schema<
       lowercase: true,
       trim: true,
     },
-    displayName: {
+    userName: {
       type: String,
       required: true,
       trim: true,