feat: restructure into XFlow monorepo with Nuxt 4, Modular Onion Monolith, Android client, and Desktop CLI

apps/web/server/core/domain/DomainError.ts

@@ -0,0 +1,29 @@
+export abstract class DomainError extends Error {
+  public abstract readonly code: string;
+  public abstract readonly statusCode: number;
+
+  constructor(message: string) {
+    super(message);
+    Object.setPrototypeOf(this, new.target.prototype);
+  }
+}
+
+export class NotFoundError extends DomainError {
+  public readonly code = 'NOT_FOUND';
+  public readonly statusCode = 404;
+}
+
+export class ValidationError extends DomainError {
+  public readonly code = 'VALIDATION_ERROR';
+  public readonly statusCode = 400;
+}
+
+export class UnauthorizedError extends DomainError {
+  public readonly code = 'UNAUTHORIZED';
+  public readonly statusCode = 401;
+}
+
+export class ForbiddenError extends DomainError {
+  public readonly code = 'FORBIDDEN';
+  public readonly statusCode = 403;
+}

apps/web/server/core/domain/Result.ts

@@ -0,0 +1,37 @@
+export class Result<T, E = Error> {
+  private constructor(
+    private readonly _isSuccess: boolean,
+    private readonly _value?: T,
+    private readonly _error?: E
+  ) {}
+
+  public static ok<U>(value: U): Result<U, never> {
+    return new Result<U, never>(true, value);
+  }
+
+  public static fail<F>(error: F): Result<never, F> {
+    return new Result<never, F>(false, undefined, error);
+  }
+
+  public get isSuccess(): boolean {
+    return this._isSuccess;
+  }
+
+  public get isFailure(): boolean {
+    return !this._isSuccess;
+  }
+
+  public getValue(): T {
+    if (!this._isSuccess) {
+      throw new Error(`Cannot get value from failed Result: ${this._error}`);
+    }
+    return this._value as T;
+  }
+
+  public getError(): E {
+    if (this._isSuccess) {
+      throw new Error("Cannot get error from successful Result");
+    }
+    return this._error as E;
+  }
+}