BIZ-42: Phase2 可观测性+WebUI+避退模式 — metrics/health/webui/dashboard/adaptive

新增文件:
- metrics.py: Prometheus 指标端点 (:9191), 10+3 个指标
- health.py: /health (liveness) + /health/ready (readiness)
- webui.py: WebUI 后端 API (SSE 实时推送 + 配置热重载)
- static/dashboard.html: 仪表盘前端 (Chart.js, 令牌桶仪表+队列柱状图+吞吐折线图)

更新文件:
- rate_limiter.py: 增加 AdaptiveTokenBucket 避退模式 (ADR-009)
  状态机 NORMAL→RETREAT→RECOVER, 429 率滑动窗口监控
- server.py: structlog 结构化日志 + 避退反馈回路
  挂载 metrics_server (:9191) + health/ready + webui + /status
- pyproject.toml: 增加 prometheus-client, pydantic, types-PyYAML 依赖

验证:
- mypy --strict: 0 issues in 7 source files
- AdaptiveTokenBucket 运行时测试通过
- 所有语法检查通过

Co-authored-by: multica-agent <github@multica.ai>

services/nvidia_sidecar/pyproject.toml

@@ -11,6 +11,8 @@ dependencies = [
     "httpx>=0.28",
     "PyYAML>=6.0",
     "structlog>=24.4",
+    "prometheus-client>=0.21",
+    "pydantic>=2.0",
 ]
 
 [project.optional-dependencies]
@@ -19,6 +21,7 @@ dev = [
     "pytest-asyncio>=0.24",
     "httpx>=0.28",
     "mypy>=1.14",
+    "types-PyYAML",
 ]
 
 [project.scripts]
@@ -28,8 +31,12 @@ nvidia-sidecar = "nvidia_sidecar.server:main"
 requires = ["setuptools>=75", "wheel"]
 build-backend = "setuptools.build_meta"
 
-[tool.setuptools.packages.find]
-where = ["."]
+[tool.setuptools]
+packages = ["nvidia_sidecar"]
+
+[tool.setuptools.package-dir]
+# Flat layout: __init__.py + all .py files at project root
+"nvidia_sidecar" = "."
 
 [tool.mypy]
 python_version = "3.12"