fix(07): UAT fixes — SMTP test email, DKV routing, Exchange domain field

- SMTP: add test-to field, send real email via sendMail() instead of verify()
- SMTP: fix no_auth warning shown as error for open-relay servers
- DKV: register dkv-fleet in MODULE_REGISTRY (fixes "Modul nicht gefunden")
- DKV: add dynamic [category]/[moduleSlug]/settings + vehicles sub-routes
- DKV: settings/vehicles links use useParams for consistent URLs
- DKV: add gear icon settings link to module main page
- DKV: rename module to "DKV-Rechnung" in seed + translations
- DKV: add optional domain field for Exchange (WebCredentials 3rd arg)
- DKV: hide IMAP-only fields (Port/Verschlüsselung/Ordner) when Exchange selected
- DKV: hide Exchange-only field (Domain) when IMAP selected
- Prisma: add domain column to DkvModuleConfig

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/api/src/settings/dto/smtp-config.dto.ts

@@ -44,4 +44,8 @@ export class SmtpConfigDto {
 
   @IsEmail()
   fromAddress!: string;
+
+  @IsOptional()
+  @IsEmail()
+  testTo?: string;
 }

apps/api/src/settings/settings.service.ts

@@ -138,8 +138,6 @@ export class SettingsService {
       }
     }
 
-    const hasAuth = !!(username && password);
-
     try {
       const transport = nodemailer.createTransport({
         host: dto.host,
@@ -154,13 +152,17 @@ export class SettingsService {
           : undefined,
       });
 
-      await transport.verify();
-
-      // T-07-16: connection passed but warn when no auth — server reachable but
-      // unauthenticated relay will likely be rejected when actually sending.
-      if (!hasAuth) {
-        return { success: true, warning: 'no_auth' };
+      if (dto.testTo) {
+        await transport.sendMail({
+          from: dto.fromAddress,
+          to: dto.testTo,
+          subject: 'Tessera SMTP-Test',
+          text: 'Diese E-Mail bestätigt, dass die SMTP-Konfiguration in Tessera funktioniert.',
+        });
+      } else {
+        await transport.verify();
       }
+
       return { success: true };
     } catch (error) {
       this.logger.warn(