feat: make runtime scanning tunable within safe bounds

.env.example

@@ -4,6 +4,12 @@ ORBIT_HTTP_ADDR=127.0.0.1:8080
 ORBIT_MYSQL_DSN=
 ORBIT_DB_MAX_OPEN=20
 ORBIT_DB_MAX_IDLE=5
+# 后台控制循环的有界调度间隔；默认 workflow/schedule=1s，recovery=2s。
+ORBIT_WORKFLOW_TICK_INTERVAL=1s
+ORBIT_SCHEDULE_TICK_INTERVAL=1s
+ORBIT_RECOVERY_TICK_INTERVAL=2s
+# 每个后台批次最多处理的持久化候选，范围1–100。
+ORBIT_RUNTIME_BATCH_LIMIT=100
 # Empty disables metrics. To enable a separate private listener, use e.g.
 # ORBIT_METRICS_ADDR=127.0.0.1:9090. Never expose it on the public API ingress.
 ORBIT_METRICS_ADDR=