feat(tenancy): add member detail modal + fix invite name saving

Merchant team page:
- Consistent member display (full_name + email on every row)
- New view button (eye icon) on all members including owner
- View modal shows account info (username, role, email verified,
  last login, account created) and store memberships with roles
- API enriched with user metadata (username, role, is_email_verified,
  last_login, created_at)

Invite fix (both merchant and store routes):
- first_name and last_name from invite form were never passed to the
  service that creates the User account. Now passed through correctly.

i18n: 6 new keys across 4 locales (view_member, account_information,
username, email_verified, last_login, account_created).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/modules/tenancy/locales/de.json

@@ -50,6 +50,12 @@
         "stores_and_roles": "Filialen & Rollen",
         "title": "Team",
         "total_members": "Mitglieder gesamt",
+        "view_member": "Mitglied anzeigen",
+        "account_information": "Kontoinformationen",
+        "username": "Benutzername",
+        "email_verified": "E-Mail verifiziert",
+        "last_login": "Letzte Anmeldung",
+        "account_created": "Konto erstellt",
         "viewer": "Betrachter"
     },
     "messages": {