Remove old configuration, API client, and redundant crypto mocks

- Deleted legacy `config` module and replaced its usage with the new runtime-validated `app.config`.
- Removed old custom Axios `apiClient` with outdated token refresh logic.
- Cleaned up redundant crypto-related mocks in storage tests and replaced them with real encryption/decryption during testing.
- Updated Jest coverage exclusions to reflect the new file structure and generated client usage.

frontend/src/lib/api/client.ts

@@ -6,7 +6,7 @@
 import axios, { AxiosError, AxiosRequestConfig, InternalAxiosRequestConfig } from 'axios';
 import { useAuthStore } from '@/stores/authStore';
 import { parseAPIError, type APIErrorResponse } from './errors';
-import config from '@/config';
+import config from '@/config/app.config';
 
 /**
  * Separate axios instance for auth endpoints