refactor(frontend): Remove '/api' prefix from all API calls to align with backend URL convention

- Updated all API endpoint strings in 'frontend/src' (via sed and manual fixes) to remove the '/api/' prefix.
- Manually fixed 'Timeline.tsx' absolute URLs to use the 'api' subdomain and correct path.
- Manually fixed 'useAuth.ts' logout fetch URLs.
- Updated 'HelpApiDocs.tsx' sandbox URL.
- This change, combined with the backend URL update, fully transitions the application to use subdomain-based routing (e.g., 'http://api.lvh.me:8000/resource/') instead of path-prefix routing (e.g., 'http://api.lvh.me:8000/api/resource/').

frontend/src/pages/HelpApiDocs.tsx

@@ -41,7 +41,7 @@ const LANGUAGES: Record<CodeLanguage, LanguageConfig> = {
 // Default test credentials (used when no tokens are available)
 const DEFAULT_TEST_API_KEY = 'ss_test_<your_test_token_here>';
 const DEFAULT_TEST_WEBHOOK_SECRET = 'whsec_test_abc123def456ghi789jkl012mno345pqr678';
-const SANDBOX_URL = 'https://sandbox.smoothschedule.com/api/v1';
+const SANDBOX_URL = 'https://sandbox.smoothschedule.com/v1';
 
 // Multi-language code interface
 interface MultiLangCode {
@@ -1111,7 +1111,7 @@ my $response = $ua->get('${SANDBOX_URL}/services/',
               )}
 
               <a
-                href="/api/v1/docs/"
+                href="/v1/docs/"
                 target="_blank"
                 rel="noopener noreferrer"
                 className="flex items-center gap-2 px-4 py-2 text-sm font-medium text-purple-600 dark:text-purple-400 hover:bg-purple-50 dark:hover:bg-purple-900/20 rounded-lg transition-colors"