feat: add Playwright E2E and API regression test suite

Production-ready test infrastructure with Page Object Model pattern,
reusable fixtures for auth/DB/test-data, and example tests covering
login flow, dashboard, accounts CRUD API, and visual regression.

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

tests/page-objects/AccountsPage.ts

@@ -0,0 +1,82 @@
+/**
+ * Page object for the Accounts page (/accounts).
+ *
+ * Maps to: frontend/src/pages/accounts/AccountsPage.tsx
+ * Data: GET /api/accounts, POST /api/accounts, PUT /api/accounts/:id
+ */
+
+import { type Page, expect } from '@playwright/test';
+import { BasePage } from './BasePage';
+
+export class AccountsPage extends BasePage {
+  readonly path = '/accounts';
+
+  // ─── Locators ────────────────────────────────────────────────
+
+  get heading() {
+    return this.page.getByRole('heading', { name: /accounts|chart of accounts/i }).first();
+  }
+
+  get addAccountButton() {
+    return this.page.getByRole('button', { name: /add|create|new/i }).first();
+  }
+
+  /** Account name input in the create/edit modal */
+  get nameInput() {
+    return this.page.getByLabel(/name/i).first();
+  }
+
+  /** Account number input */
+  get numberInput() {
+    return this.page.getByLabel(/number/i).first();
+  }
+
+  /** Account type select */
+  get typeSelect() {
+    return this.page.getByLabel(/type/i).first();
+  }
+
+  /** Save/submit button in modal */
+  get saveButton() {
+    return this.page.getByRole('button', { name: /save|create|submit/i }).first();
+  }
+
+  /** Cancel button in modal */
+  get cancelButton() {
+    return this.page.getByRole('button', { name: /cancel/i }).first();
+  }
+
+  // ─── Actions ─────────────────────────────────────────────────
+
+  override async waitForReady(): Promise<void> {
+    await this.page.waitForLoadState('networkidle');
+    // Wait for the accounts list or heading to be visible
+    await expect(this.page.locator('main')).toBeVisible();
+  }
+
+  /** Get the count of visible account rows */
+  async getAccountCount(): Promise<number> {
+    return this.tableRows.count();
+  }
+
+  /** Find an account row by name */
+  accountRow(name: string) {
+    return this.tableBody.locator('tr').filter({ hasText: name });
+  }
+
+  /** Assert an account exists in the table */
+  async assertAccountExists(name: string): Promise<void> {
+    await expect(this.accountRow(name)).toBeVisible();
+  }
+
+  /** Assert an account does NOT exist in the table */
+  async assertAccountNotExists(name: string): Promise<void> {
+    await expect(this.accountRow(name)).not.toBeVisible();
+  }
+
+  /** Open the create account modal */
+  async openCreateModal(): Promise<void> {
+    await this.addAccountButton.click();
+    await expect(this.nameInput).toBeVisible();
+  }
+}