feat: add testing infrastructure — Vitest, Playwright, CI, git hooks

Add comprehensive testing covering 420 unit/handler tests across 24 Vitest
files, 9 Playwright E2E specs, accessibility scans, and visual regression.
Includes GitHub Actions CI, Husky pre-push hook, and TESTING.md docs.

e2e/admin-members.spec.js

@@ -0,0 +1,48 @@
+import { test, expect } from './helpers/fixtures.js'
+
+test.describe('Admin members page', () => {
+  test('members list loads for admin', async ({ adminPage }) => {
+    await adminPage.goto('/admin/members')
+
+    await expect(adminPage.locator('h1')).toHaveText('Members')
+    await expect(adminPage.getByText('Manage members, contributions, and access')).toBeVisible()
+  })
+
+  test('search bar works', async ({ adminPage }) => {
+    await adminPage.goto('/admin/members')
+
+    const searchInput = adminPage.getByPlaceholder('Search members...')
+    await expect(searchInput).toBeVisible()
+
+    await searchInput.fill('nonexistent-query-xyz')
+
+    // Page should not crash -- either shows filtered results or the empty state
+    await expect(
+      adminPage.locator('table').or(adminPage.getByText('No members found matching your criteria'))
+    ).toBeVisible()
+  })
+
+  test('non-admin redirect', async ({ browser }) => {
+    const context = await browser.newContext()
+    const page = await context.newPage()
+
+    await page.goto('/admin/members')
+
+    // Admin middleware redirects non-admin users to / or /members
+    await page.waitForURL((url) => !url.pathname.startsWith('/admin'))
+    expect(page.url()).not.toContain('/admin/members')
+
+    await context.close()
+  })
+
+  test('add member button opens modal', async ({ adminPage }) => {
+    await adminPage.goto('/admin/members')
+
+    await adminPage.getByRole('button', { name: 'Add Member' }).click()
+
+    // Modal should appear with the form heading and fields
+    await expect(adminPage.getByText('Add New Member')).toBeVisible()
+    await expect(adminPage.getByPlaceholder('Full name')).toBeVisible()
+    await expect(adminPage.getByPlaceholder('email@example.com')).toBeVisible()
+  })
+})