feat(infra): transactional outbox — OutboxWriter port, PgOutboxWriter, OutboxRelay, TestOutbox; update create_thought + delete_thought

crates/adapters/postgres/migrations/011_outbox_events.sql

@@ -0,0 +1,10 @@
+CREATE TABLE outbox_events (
+    seq          BIGSERIAL   PRIMARY KEY,
+    aggregate_id UUID        NOT NULL,
+    event_type   TEXT        NOT NULL,
+    payload      JSONB       NOT NULL,
+    created_at   TIMESTAMPTZ NOT NULL DEFAULT now(),
+    delivered    BOOLEAN     NOT NULL DEFAULT false,
+    delivered_at TIMESTAMPTZ
+);
+CREATE INDEX outbox_events_pending_idx ON outbox_events (seq) WHERE delivered = false;