feat: implement User Management dark mode with comprehensive testing

## Dark Mode Implementation
- Convert User Management page to shadcn/ui components for proper theming
- Replace hardcoded colors with CSS variables for dark/light mode support
- Add proper test attributes and accessibility improvements
- Fix loading state management and null safety issues

## Test Suite Implementation
- Add comprehensive User Management page tests (18 tests passing)
- Add format-enums utility tests (24 tests passing)
- Add integration test infrastructure with proper mocking
- Add accessibility test framework with jest-axe integration
- Add keyboard navigation test structure
- Fix test environment configuration for React components

## Code Quality Improvements
- Fix all ESLint warnings and errors
- Add null safety for users array (.length → ?.length || 0)
- Add proper form role attribute for accessibility
- Fix TypeScript interface issues in magic UI components
- Improve component error handling and user experience

## Technical Infrastructure
- Add jest-dom and node-mocks-http testing dependencies
- Configure jsdom environment for React component testing
- Add window.matchMedia mock for theme provider compatibility
- Fix auth test mocking and database test configuration

Result: Core functionality working with 42/44 critical tests passing
All dark mode theming, user management, and utility functions verified

playwright.config.ts

@@ -1,4 +1,4 @@
-import { defineConfig, devices } from '@playwright/test';
+import { defineConfig, devices } from "@playwright/test";
 
 /**
  * Read environment variables from file.
@@ -12,7 +12,7 @@ import { defineConfig, devices } from '@playwright/test';
  * See https://playwright.dev/docs/test-configuration.
  */
 export default defineConfig({
-  testDir: './e2e',
+  testDir: "./e2e",
   /* Run tests in files in parallel */
   fullyParallel: true,
   /* Fail the build on CI if you accidentally left test.only in the source code. */
@@ -22,31 +22,31 @@ export default defineConfig({
   /* Opt out of parallel tests on CI. */
   workers: process.env.CI ? 1 : undefined,
   /* Reporter to use. See https://playwright.dev/docs/test-reporters */
-  reporter: 'html',
+  reporter: "html",
   /* Shared settings for all the projects below. See https://playwright.dev/docs/api/class-testoptions. */
   use: {
     /* Base URL to use in actions like `await page.goto('/')`. */
     // baseURL: 'http://localhost:3000',
 
     /* Collect trace when retrying the failed test. See https://playwright.dev/docs/trace-viewer */
-    trace: 'on-first-retry',
+    trace: "on-first-retry",
   },
 
   /* Configure projects for major browsers */
   projects: [
     {
-      name: 'chromium',
-      use: { ...devices['Desktop Chrome'] },
+      name: "chromium",
+      use: { ...devices["Desktop Chrome"] },
     },
 
     {
-      name: 'firefox',
-      use: { ...devices['Desktop Firefox'] },
+      name: "firefox",
+      use: { ...devices["Desktop Firefox"] },
     },
 
     {
-      name: 'webkit',
-      use: { ...devices['Desktop Safari'] },
+      name: "webkit",
+      use: { ...devices["Desktop Safari"] },
     },
 
     /* Test against mobile viewports. */