phase 2 (part 2): sqlc queries, audit/event helpers, event NOTIFY trigger

- sqlc.yaml + internal/db/queries/*.sql: typed queries for entities,
  relationships, ontology, operations (signals, events, audit,
  idempotency, entity_status)
- internal/db/sqlcgen/: generated Go from sqlc (pgx/v5)
- internal/observability/record.go: Audit() and Event() helpers that
  write in the caller's transaction (SG10). actorLabel is interim text
  identity in detail JSON until OIDC resolution lands; actor_id column
  exists but is not yet populated
- migrations/008: post-commit pg_notify trigger on events table for
  SSE fan-out (SG8/SG10)

internal/db/queries/ontology.sql

@@ -0,0 +1,13 @@
+-- name: ListEntityTypes :many
+SELECT * FROM entity_types ORDER BY name;
+
+-- name: ListRelationshipTypes :many
+SELECT * FROM relationship_types ORDER BY name;
+
+-- name: ListLifecycleDefs :many
+SELECT * FROM lifecycle_defs ORDER BY id;
+
+-- name: GetLifecycleForType :one
+SELECT ld.* FROM lifecycle_defs ld
+JOIN entity_types et ON et.lifecycle_id = ld.id
+WHERE et.name = $1;