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.

server/api/members/[id]/create-portal-account.post.ts

@@ -122,7 +122,7 @@ export default defineEventHandler(async (event) => {
       const { getEmailService } = await import('~/server/utils/email');
       const { generateEmailVerificationToken } = await import('~/server/utils/email-tokens');
       
-      const emailService = getEmailService();
+        const emailService = await getEmailService();
       const verificationToken = await generateEmailVerificationToken(keycloakId, member.email);
       const config = useRuntimeConfig();
       const verificationLink = `${config.public.domain}/api/auth/verify-email?token=${verificationToken}`;