feat(backend): 搭建 FastAPI 分层骨架 — 配置加载 / 健康检查 / SQLAlchemy+Alembic 就位

- uv 工程（Python 3.12，pyproject + uv.lock，dev: pytest/ruff）
- 分层包结构：api / application / domain / infrastructure / quant(qlib_adapter) / agent / core
- app.core.config：加载根 config.yaml + .env，sqlite 相对路径解析到项目根 data/
- SQLAlchemy Base + Session 工厂（Infrastructure 层，业务走 Repository）
- Alembic 迁移环境就位（env.py 复用应用配置，render_as_batch 兼容 SQLite）
- GET /api/health + pytest 冒烟 6 项通过 / ruff clean / uvicorn 启动验证

backend/pyproject.toml

@@ -0,0 +1,38 @@
+[project]
+name = "qlib-platform-backend"
+version = "0.1.0"
+description = "A股个人量化研究平台后端：Qlib 研究引擎 / Tushare 数据源 / FastAPI"
+readme = "../README.md"
+requires-python = ">=3.12"
+dependencies = [
+    "fastapi>=0.115",
+    "uvicorn[standard]>=0.32",
+    "sqlalchemy>=2.0",
+    "alembic>=1.13",
+    "pyyaml>=6.0",
+]
+
+[dependency-groups]
+dev = [
+    "pytest>=8.0",
+    "httpx>=0.27",
+    "ruff>=0.6",
+]
+
+# uv：本项目是应用（backend/app），不作为可分发包构建
+[tool.uv]
+package = false
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+pythonpath = ["."]
+addopts = "-q"
+
+[tool.ruff]
+line-length = 100
+target-version = "py312"
+src = ["app", "tests"]
+
+[tool.ruff.lint]
+select = ["E", "F", "I", "UP", "B", "SIM"]
+ignore = ["E501"]