feat: event store — persist domain events to Postgres event_log table via composite publisher

crates/adapters/postgres/migrations/010_event_log.sql

@@ -0,0 +1,10 @@
+CREATE TABLE IF NOT EXISTS event_log (
+    event_id    BIGSERIAL PRIMARY KEY,
+    aggregate_id UUID NOT NULL,
+    event_type  TEXT NOT NULL,
+    payload     JSONB NOT NULL,
+    occurred_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+CREATE INDEX idx_event_log_aggregate ON event_log (aggregate_id);
+CREATE INDEX idx_event_log_type      ON event_log (event_type);
+CREATE INDEX idx_event_log_occurred  ON event_log (occurred_at);