feat: 性能监控基础设施、解密缓存及计费简化

- 新增 PerfRecorder 性能记录工具，支持采样率与慢请求日志
- 在请求管道中埋点：auth、body_read、json_parse、context_build、authorize、handle
- 流处理器增加 parse/conversion 耗时追踪与 perf_metrics 落库
- 解密服务添加 LRU 缓存，降低高频解密 CPU 开销
- 格式转换分层开关设计：全局 OFF 时回退到端点配置，而非一刀切拒绝
- 移除 shadow billing 模块，统一使用新计费引擎
- 新增 Codex 网关请求适配器（store=false、role 映射、include 补齐）
- endpoint 创建接口支持 body_rules 参数

tests/services/test_format_conversion_candidate_selection.py

@@ -67,7 +67,11 @@ async def test_build_candidates_allows_cross_format_when_endpoint_accepts_and_ov
 
 
 @pytest.mark.asyncio
-async def test_build_candidates_blocks_cross_format_when_master_switch_off() -> None:
+async def test_build_candidates_allows_cross_format_when_global_off_but_endpoint_enabled() -> None:
+    """
+    分层开关设计：全局 OFF 时回退到端点配置
+    - 全局 OFF + 端点 enabled=True -> 允许（端点覆盖全局默认）
+    """
     register_default_normalizers()
 
     scheduler = CacheAwareScheduler()
@@ -85,6 +89,40 @@ async def test_build_candidates_blocks_cross_format_when_master_switch_off() ->
     ]
     provider.api_keys = [_mock_key("k1", ["openai:chat"])]
 
+    candidates = await scheduler._build_candidates(
+        db=MagicMock(),
+        providers=[provider],
+        client_format="claude:chat",
+        model_name="dummy-model",
+        affinity_key=None,
+        global_conversion_enabled=False,  # 全局开关关闭，但端点配置允许
+    )
+
+    # 新设计：全局 OFF 时回退到端点配置，端点 enabled=True 则允许
+    assert len(candidates) == 1
+    assert candidates[0].needs_conversion is True
+    assert candidates[0].provider_api_format == "openai:chat"
+
+
+@pytest.mark.asyncio
+async def test_build_candidates_blocks_cross_format_when_global_off_and_endpoint_not_configured() -> (
+    None
+):
+    """
+    分层开关设计：全局 OFF + 端点未配置 -> 阻止
+    """
+    register_default_normalizers()
+
+    scheduler = CacheAwareScheduler()
+    scheduler._check_model_support = AsyncMock(return_value=(True, None, None, {"m"}))  # type: ignore[method-assign]
+    scheduler._check_key_availability = MagicMock(return_value=(True, None, None))  # type: ignore[method-assign]
+
+    provider = MagicMock()
+    provider.name = "p1"
+    provider.enable_format_conversion = False
+    provider.endpoints = [_mock_endpoint("openai:chat", None)]  # 端点未配置格式接受策略
+    provider.api_keys = [_mock_key("k1", ["openai:chat"])]
+
     candidates = await scheduler._build_candidates(
         db=MagicMock(),
         providers=[provider],
@@ -94,6 +132,7 @@ async def test_build_candidates_blocks_cross_format_when_master_switch_off() ->
         global_conversion_enabled=False,  # 全局开关关闭
     )
 
+    # 全局 OFF + 端点未配置 -> 阻止
     assert candidates == []