openai service and basic tables with migrations

db/migrations/20260102021829_wa_messages.sql

@@ -0,0 +1,24 @@
+-- migrate:up
+create table wa_messages (
+  id bigserial primary key,
+  tenant_id uuid not null references tenants(id) on delete cascade,
+  wa_chat_id text not null,
+
+  provider text not null,          -- sim / evolution / twilio
+  message_id text not null,        -- idempotencia por provider
+  direction text not null,         -- in / out
+
+  ts timestamptz not null default now(),
+  text text null,
+  payload jsonb not null default '{}'::jsonb,
+
+  run_id uuid null,
+
+  unique (tenant_id, provider, message_id)
+);
+
+create index idx_msgs_tenant_chat_ts
+  on wa_messages (tenant_id, wa_chat_id, ts desc);
+
+-- migrate:down
+drop table if exists wa_messages;