Refactor to enforce AuthContext usage over useAuthStore and improve test stability

- Replaced `useAuthStore` with `useAuth` from `AuthContext` across frontend components and tests to ensure dependency injection compliance.
- Enhanced E2E test stability by delaying navigation until the auth context is fully initialized.
- Updated Playwright configuration to use a single worker to prevent mock conflicts.
- Refactored test setup to consistently inject `AuthProvider` for improved isolation and mocking.
- Adjusted comments and documentation to clarify dependency injection and testability patterns.

frontend/src/components/auth/AuthInitializer.tsx

@@ -7,7 +7,7 @@
 'use client';
 
 import { useEffect } from 'react';
-import { useAuthStore } from '@/lib/stores/authStore';
+import { useAuth } from '@/lib/auth/AuthContext';
 
 /**
  * AuthInitializer - Initializes auth state from encrypted storage on mount
@@ -15,6 +15,9 @@ import { useAuthStore } from '@/lib/stores/authStore';
  * This component should be included in the app's Providers to ensure
  * authentication state is restored from storage when the app loads.
  *
+ * IMPORTANT: Uses useAuth() to respect dependency injection for testability.
+ * Do NOT import useAuthStore directly - it bypasses the Context wrapper.
+ *
  * @example
  * ```tsx
  * // In app/providers.tsx
@@ -29,9 +32,14 @@ import { useAuthStore } from '@/lib/stores/authStore';
  * ```
  */
 export function AuthInitializer() {
-  const loadAuthFromStorage = useAuthStore((state) => state.loadAuthFromStorage);
+  const loadAuthFromStorage = useAuth((state) => state.loadAuthFromStorage);
 
   useEffect(() => {
+    // Skip loading from storage in E2E tests - test store is already injected
+    if (typeof window !== 'undefined' && (window as any).__E2E_TEST__) {
+      return;
+    }
+
     // Load auth state from encrypted storage on mount
     loadAuthFromStorage();
   }, [loadAuthFromStorage]);