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/web/src/messages/en.json

@@ -133,6 +133,9 @@
       "test": "Test Connection",
       "showPassword": "Show password",
       "hidePassword": "Hide password",
+      "testToLabel": "Send test email to",
+      "testToPlaceholder": "recipient@example.com",
+      "testToHelp": "Optional — sends a real test email to this address.",
       "testTesting": "Testing connection...",
       "testSuccess": "Connection successful",
       "testFailed": "Connection failed"
@@ -257,7 +260,7 @@
     "error": "Error checking domain"
   },
   "dkvFleet": {
-    "pageTitle": "DKV Fleet",
+    "pageTitle": "DKV Invoice",
     "checkNow": "Check Now",
     "checking": "Checking...",
     "lastChecked": "Last checked: {time}",
@@ -309,6 +312,9 @@
     "form": {
       "protocol": "Protocol",
       "host": "Host",
+      "hostExchange": "EWS URL",
+      "domain": "Domain",
+      "domainHelp": "Optional — Windows domain (e.g. CONTOSO). Leave blank if not required.",
       "port": "Port",
       "encryption": "Encryption",
       "encryptionNone": "None",