feat(tenancy): add merchant team CRUD with multi-store hub view

The merchant team page was read-only. Now merchant owners can invite,
edit roles, and remove team members across all their stores from a
single hub view.

Architecture: No new models — delegates to existing store_team_service.
Members are deduplicated across stores with per-store role badges.

New:
- 5 API endpoints: GET team (member-centric), GET store roles, POST
  invite (multi-store), PUT update role, DELETE remove member
- merchant-team.js Alpine component with invite/edit/remove modals
- Full CRUD template with stats cards, store filter, member table
- 7 Pydantic schemas for merchant team request/response
- 2 service methods: validate_store_ownership, get_merchant_team_members
- 25 new i18n keys across 4 tenancy locales + 1 core common key

Tests: 434 tenancy tests passing, arch-check green.

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

app/modules/tenancy/locales/de.json

@@ -12,20 +12,45 @@
         "team": "Team"
     },
     "team": {
-        "title": "Team",
-        "members": "Mitglieder",
+        "actions": "Aktionen",
+        "active": "Aktiv",
         "add_member": "Mitglied hinzufügen",
+        "all_stores": "Alle Filialen",
+        "edit_member": "Mitglied bearbeiten",
+        "editor": "Bearbeiter",
+        "email": "E-Mail",
+        "email_placeholder": "E-Mail-Adresse eingeben",
+        "error_title": "Fehler beim Laden des Teams",
+        "first_name": "Vorname",
+        "invite_first_member": "Laden Sie Ihr erstes Teammitglied ein",
         "invite_member": "Mitglied einladen",
+        "invitation_accepted": "Einladung angenommen",
+        "invitation_sent": "Einladung gesendet",
+        "last_name": "Nachname",
+        "loading_team": "Team wird geladen...",
+        "manage_members_description": "Teammitglieder über alle Filialen verwalten",
+        "manager": "Manager",
+        "member": "Mitglied",
+        "member_stores": "Filialen des Mitglieds",
+        "members": "Mitglieder",
+        "no_members_description": "Laden Sie Teammitglieder ein um Ihre Filialen zu verwalten",
+        "no_members_title": "Noch keine Teammitglieder",
+        "no_role": "Keine Rolle",
+        "owner": "Inhaber",
+        "pending_invitations": "Ausstehende Einladungen",
+        "permissions": "Berechtigungen",
+        "remove_confirmation": "Sind Sie sicher, dass Sie entfernen möchten",
+        "remove_from_all_stores": "Aus allen Filialen entfernen",
         "remove_member": "Mitglied entfernen",
         "role": "Rolle",
-        "owner": "Inhaber",
-        "manager": "Manager",
-        "editor": "Bearbeiter",
-        "viewer": "Betrachter",
-        "permissions": "Berechtigungen",
-        "pending_invitations": "Ausstehende Einladungen",
-        "invitation_sent": "Einladung gesendet",
-        "invitation_accepted": "Einladung angenommen"
+        "select_stores": "Filialen auswählen",
+        "send_invitation": "Einladung senden",
+        "status": "Status",
+        "store_roles": "Filialrollen",
+        "stores_and_roles": "Filialen & Rollen",
+        "title": "Team",
+        "total_members": "Mitglieder gesamt",
+        "viewer": "Betrachter"
     },
     "messages": {
         "business_info_saved": "Business info saved",