feat: 流式空闲超时、健康监控查询优化、限流桶内存上限与维护清理修复

Close #233

Co-authored-by: AAEE86 <ppk0227@hotmail.com>

- cli_monitor_mixin: 引入 STREAM_IDLE_TIMEOUT_SECONDS（可通过环境变量配置），
  流传输开始后若超出空闲窗口无新 chunk 则提前取消并返回 504，避免长时间挂起
- stream_context: 新增 managed_recorded_bodies 上下文管理器，确保 chunks 在
  telemetry 完成后及时释放；stream_telemetry 使用该接口统一管理 response body 构建
- health endpoint: 将状态聚合改为 GROUP BY 直接统计，事件列表按 api_format
  单独查询，避免单次 limit 拉取大量记录导致的遗漏与性能问题；同时过滤不活跃
  provider/endpoint，与公开健康接口保持一致
- endpoint health service: 修正时间线数据按 endpoint_id 而非 key_id 聚合
- token_bucket: 引入 max_buckets/bucket_expiry 上限与定时清理，防止内存无限增长；
  修复 refill_rate=0 时 get_reset_time 除零异常；新增 _is_unlimited_rate_limit 判断
- maintenance_scheduler: 调整清理顺序（先删整行再按窗口清理），新增 newer_than
  边界参数，避免同一行在同一轮中被重复改写
- sync_execute: 新增 create_pending_usage 开关，允许已预创建记录的调用方跳过重复创建
- quota_reader / provider_ops balance: 小幅修复与健壮性提升
- Dockerfile: 添加 MALLOC_ARENA_MAX=2 环境变量以降低 gunicorn worker RSS
- 补充相关测试覆盖

tests/plugins/test_manager.py

@@ -0,0 +1,50 @@
+import os
+
+import pytest
+
+os.environ.setdefault("JWT_SECRET_KEY", "test-secret-key")
+
+from src.plugins.manager import PluginManager
+
+
+def _build_manager() -> PluginManager:
+    return PluginManager(
+        config={
+            "auth": {"api_key": False},
+            "cache": {"memory": False},
+            "monitor": {"prometheus": False},
+            "token": {"claude": False},
+            "load_balancer": {"sticky_priority": False},
+        }
+    )
+
+
+def test_rate_limit_defaults_to_token_bucket_when_unconfigured() -> None:
+    manager = _build_manager()
+
+    plugin = manager.get_plugin("rate_limit")
+
+    assert plugin is not None
+    assert plugin.name == "token_bucket"
+
+
+@pytest.mark.asyncio
+async def test_default_rate_limit_plugin_honors_dynamic_rate_limit() -> None:
+    manager = _build_manager()
+
+    plugin = manager.get_plugin("rate_limit")
+
+    assert plugin is not None
+
+    first = await plugin.check_limit("public_ip:test", rate_limit=2)
+    assert first.allowed is True
+    await plugin.consume("public_ip:test", amount=1, rate_limit=2)
+
+    second = await plugin.check_limit("public_ip:test", rate_limit=2)
+    assert second.allowed is True
+    await plugin.consume("public_ip:test", amount=1, rate_limit=2)
+
+    third = await plugin.check_limit("public_ip:test", rate_limit=2)
+    assert third.allowed is False
+    assert third.remaining == 0
+    assert third.retry_after is not None