feat: tabela tenant_members + primeiro admin seed

- tenant_members mapeia auth.users a um tenant com role
- RLS: members_read_own (user ve so os tenants dos quais participa)
- Seed manual: admin@reserva.test (senha Admin1234!) associado ao
  tenant grupo-1001 como admin

supabase/migrations/20260414000004_tenant_members.sql

@@ -0,0 +1,25 @@
+-- Tenant members: mapeia usuarios auth.users a um tenant com role
+-- Já aplicada via MCP.
+
+create table if not exists reserva_hotel.tenant_members (
+  id          bigserial primary key,
+  tenant_id   bigint not null references reserva_hotel.tenants(id) on delete cascade,
+  user_id     uuid not null,
+  role        text not null default 'admin',
+  created_at  timestamptz not null default now(),
+  unique (tenant_id, user_id)
+);
+
+create index if not exists idx_tenant_members_user on reserva_hotel.tenant_members(user_id);
+create index if not exists idx_tenant_members_tenant on reserva_hotel.tenant_members(tenant_id);
+
+alter table reserva_hotel.tenant_members enable row level security;
+
+drop policy if exists "members_read_own" on reserva_hotel.tenant_members;
+create policy "members_read_own" on reserva_hotel.tenant_members
+  for select using (auth.uid() = user_id);
+
+grant select on reserva_hotel.tenant_members to authenticated;
+
+-- Seed: admin@reserva.test (criado via Auth API) é membro do tenant grupo-1001
+-- INSERT executado manualmente apos criar o user via /auth/v1/signup.