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/billing/test_shadow_billing.py

@@ -1,112 +0,0 @@
-from unittest.mock import MagicMock
-
-import pytest
-
-from src.config.settings import config
-from src.services.billing.schema import BillingSnapshot, CostResult
-from src.services.billing.shadow import CostBreakdown, ShadowBillingService
-
-
-class TestShadowBillingServiceModeResolution:
-    def test_get_engine_mode_exact_and_wildcard(self, monkeypatch: pytest.MonkeyPatch) -> None:
-        monkeypatch.setattr(config, "billing_engine", "legacy", raising=False)
-        monkeypatch.setattr(
-            config,
-            "billing_engine_overrides",
-            '{"anthropic/*": "shadow", "openai/gpt-4o": "new"}',
-            raising=False,
-        )
-
-        svc = ShadowBillingService(MagicMock())
-        assert svc.get_engine_mode("openai", "gpt-4o") == "new"
-        assert svc.get_engine_mode("anthropic", "claude-3-5-sonnet") == "shadow"
-        assert svc.get_engine_mode("other", "x") == "legacy"
-
-
-class TestShadowBillingServiceExecution:
-    def test_legacy_mode_skips_new_engine(self, monkeypatch: pytest.MonkeyPatch) -> None:
-        monkeypatch.setattr(config, "billing_engine", "legacy", raising=False)
-        monkeypatch.setattr(config, "billing_engine_overrides", "{}", raising=False)
-
-        svc = ShadowBillingService(MagicMock())
-        # Guard: if new engine calculate gets called, fail.
-        svc._new_billing = MagicMock()
-        svc._new_billing.calculate.side_effect = AssertionError(
-            "new engine should not run in legacy mode"
-        )
-
-        legacy_truth = CostBreakdown(
-            input_cost=0.1,
-            output_cost=0.2,
-            cache_creation_cost=0.0,
-            cache_read_cost=0.0,
-            request_cost=0.0,
-            total_cost=0.3,
-        )
-
-        res = svc.calculate_with_shadow(
-            provider="openai",
-            provider_id="p-1",
-            model="gpt-4o",
-            task_type="chat",
-            api_format="openai:chat",
-            input_tokens=1,
-            output_tokens=1,
-            legacy_truth=legacy_truth,
-            is_failed_request=False,
-        )
-
-        assert res.engine_mode == "legacy"
-        assert res.truth_engine == "legacy"
-        assert res.shadow_snapshot is None
-        assert res.truth_breakdown.total_cost == 0.3
-
-    def test_shadow_mode_returns_snapshot_and_keeps_legacy_truth(
-        self, monkeypatch: pytest.MonkeyPatch
-    ) -> None:
-        monkeypatch.setattr(config, "billing_engine", "shadow", raising=False)
-        monkeypatch.setattr(config, "billing_engine_overrides", "{}", raising=False)
-        monkeypatch.setattr(config, "billing_diff_threshold_usd", 0.0001, raising=False)
-
-        svc = ShadowBillingService(MagicMock())
-
-        # Stub new engine output
-        snapshot = BillingSnapshot(
-            resolved_dimensions={"input_tokens": 1},
-            resolved_variables={"input_price_per_1m": "3.0"},
-            cost_breakdown={"input_cost": 0.003},
-            total_cost=0.003,
-            status="complete",
-            calculated_at="2026-02-02T00:00:00Z",
-        )
-        svc._new_billing = MagicMock()
-        svc._new_billing.calculate.return_value = CostResult(
-            cost=0.003, status="complete", snapshot=snapshot
-        )
-
-        legacy_truth = CostBreakdown(
-            input_cost=0.004,
-            output_cost=0.0,
-            cache_creation_cost=0.0,
-            cache_read_cost=0.0,
-            request_cost=0.0,
-            total_cost=0.004,
-        )
-
-        res = svc.calculate_with_shadow(
-            provider="openai",
-            provider_id="p-1",
-            model="gpt-4o",
-            task_type="chat",
-            api_format="openai:chat",
-            input_tokens=1,
-            output_tokens=0,
-            legacy_truth=legacy_truth,
-            is_failed_request=False,
-        )
-
-        assert res.engine_mode == "shadow"
-        assert res.truth_engine == "legacy"
-        assert res.shadow_snapshot is not None
-        assert res.truth_breakdown.total_cost == 0.004
-        assert "diff_usd" in res.comparison