fix(build): allow fallback select without link_clicks and ensure unique constraint in creative_pipeline

sql/creative_pipeline.sql

@@ -48,6 +48,15 @@ create unique index if not exists creative_pipeline_tenant_ref_idx
   on public.creative_pipeline (tenant_id, external_ref)
   where external_ref is not null;
 
+do $$ begin
+  if not exists (
+    select 1 from pg_constraint where conname = 'creative_pipeline_tenant_ref_uniq'
+  ) then
+    alter table public.creative_pipeline
+      add constraint creative_pipeline_tenant_ref_uniq unique (tenant_id, external_ref);
+  end if;
+end $$;
+
 create index if not exists creative_pipeline_tenant_month_idx
   on public.creative_pipeline (tenant_id, month, status);