feat(03-02): add domaincheck frontend - input form, results display, i18n

- DomainInput component with text input and submit button
- ResultList component with green/red status badges (D-01)
- checkDomainAction fetches POST /modules/domaincheck/check with auth cookie
- Page renders within portal AppShell at /modules/domaincheck
- i18n keys added for both DE and EN locales

apps/web/src/messages/de.json

@@ -134,5 +134,16 @@
   "locale": {
     "de": "Deutsch",
     "en": "English"
+  },
+  "domaincheck": {
+    "title": "Domaincheck",
+    "description": "Pruefe ob eine Domain verfuegbar ist",
+    "inputPlaceholder": "Domain eingeben (z.B. beispiel)",
+    "checkButton": "Pruefen",
+    "statusAvailable": "Verfuegbar",
+    "statusRegistered": "Registriert",
+    "noResults": "Gib einen Domain-Namen ein um die Verfuegbarkeit zu pruefen",
+    "checking": "Pruefe...",
+    "error": "Fehler bei der Pruefung"
   }
 }

apps/web/src/messages/en.json

@@ -133,5 +133,16 @@
   "locale": {
     "de": "Deutsch",
     "en": "English"
+  },
+  "domaincheck": {
+    "title": "Domain Check",
+    "description": "Check if a domain is available",
+    "inputPlaceholder": "Enter domain (e.g. example)",
+    "checkButton": "Check",
+    "statusAvailable": "Available",
+    "statusRegistered": "Registered",
+    "noResults": "Enter a domain name to check availability",
+    "checking": "Checking...",
+    "error": "Error checking domain"
   }
 }