feat: add crm webhook worker

supabase/migrations/202606290010_crm_worker_hardening.sql

@@ -0,0 +1,16 @@
+alter table public.crm_webhook_queue
+  add column if not exists provider text,
+  add column if not exists last_attempt_at timestamptz,
+  add column if not exists last_response_summary text;
+
+do $$
+begin
+  if not exists (select 1 from pg_constraint where conname = 'crm_webhook_queue_status_check') then
+    alter table public.crm_webhook_queue
+      add constraint crm_webhook_queue_status_check
+      check (status in ('pending', 'processing', 'retrying', 'sent', 'failed', 'discarded'));
+  end if;
+end $$;
+
+create index if not exists idx_crm_queue_due
+  on public.crm_webhook_queue(tenant_id, status, scheduled_at, next_attempt_at);