feat(httpapi): add local audit log with portal dual-write

Локальный audit_log (миграции pg/sqlite), GET /v1/audit, запись на CRUD и async push в auth-portal (source_app=bgp).

Co-authored-by: Cursor <cursoragent@cursor.com>

migrations/postgres/000030_audit_log.down.sql

@@ -0,0 +1,4 @@
+DROP INDEX IF EXISTS idx_audit_log_tenant_action;
+DROP INDEX IF EXISTS idx_audit_log_tenant_created;
+DROP INDEX IF EXISTS idx_audit_log_event_id;
+DROP TABLE IF EXISTS audit_log;