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/schemas/__init__.py

@@ -118,6 +118,12 @@ from app.modules.tenancy.schemas.team import (
     InvitationAccept,
     InvitationAcceptResponse,
     InvitationResponse,
+    MerchantTeamInvite,
+    MerchantTeamInviteResponse,
+    MerchantTeamMemberResponse,
+    MerchantTeamMemberStoreInfo,
+    MerchantTeamOverviewResponse,
+    MerchantTeamStoreInfo,
     PermissionCheckRequest,
     PermissionCheckResponse,
     RoleBase,