Make email service initialization asynchronous

Convert getEmailService() to async function and update all callers to use await.
Replace synchronous require() with dynamic import() for admin-config module.
Add SMTP config loading to admin configuration dialog.

components/AdminConfigurationDialog.vue

@@ -673,6 +673,12 @@ const loadConfigurations = async () => {
     if (registrationResponse.success && registrationResponse.data) {
       registrationForm.value = { ...registrationResponse.data };
     }
+
+    // Load SMTP/Email config
+    const smtpResponse = await $fetch<{ success: boolean; data?: SMTPConfig }>('/api/admin/smtp-config');
+    if (smtpResponse.success && smtpResponse.data) {
+      emailForm.value = { ...smtpResponse.data };
+    }
   } catch (error) {
     console.error('Failed to load configurations:', error);
     errorMessage.value = 'Failed to load current settings';