feat: Phase 4 — Experiment 自动归档 + 异步 Job（状态机 / SSE / 一键复跑）

- 数据表：job / experiment（spec/result JSON 存档、code_version），Alembic 迁移 53113c80257f
- Job：queued→running→(success|failed) 状态机，BackgroundTasks 本地执行 + 失败兜底标记；结果与 Experiment 关联
- Experiment：每次研究成功自动归档（含 git commit 与收益摘要），支持一键复跑（同 spec 重建 Job）
- API：POST /api/jobs、GET /api/jobs/{id}（内嵌结果）、SSE /api/jobs/{id}/events、/api/experiments 列表/详情/rerun
- 前端：新增「实验」页（列表 / 详情 / 复跑 + Job 轮询）；导航更新
- 端到端验证：真实 20 股 job 提交→后台执行→success→EXP 归档（-12.41%）；executor 成功/失败路径单测
- 测试 73 passed（新增 5 项 Job/Experiment）/ ruff clean / 前端 tsc + build 通过

backend/app/infrastructure/persistence/sqlalchemy/models/jobs.py

@@ -0,0 +1,40 @@
+"""Phase 4：Job（异步任务）与 Experiment（实验归档）表。"""
+
+from __future__ import annotations
+
+from datetime import datetime
+
+from sqlalchemy import DateTime, String, Text
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.infrastructure.persistence.sqlalchemy.base import Base
+
+
+class JobModel(Base):
+    __tablename__ = "job"
+
+    id: Mapped[str] = mapped_column(String(32), primary_key=True)
+    kind: Mapped[str] = mapped_column(String(16))
+    status: Mapped[str] = mapped_column(String(12), index=True)
+    stage: Mapped[str | None] = mapped_column(String(24), nullable=True)
+    spec_json: Mapped[str] = mapped_column(Text)
+    error: Mapped[str | None] = mapped_column(Text, nullable=True)
+    result_json: Mapped[str | None] = mapped_column(Text, nullable=True)
+    experiment_id: Mapped[str | None] = mapped_column(String(32), nullable=True)
+    created_at: Mapped[datetime] = mapped_column(DateTime)
+    started_at: Mapped[datetime | None] = mapped_column(DateTime, nullable=True)
+    finished_at: Mapped[datetime | None] = mapped_column(DateTime, nullable=True)
+
+
+class ExperimentModel(Base):
+    __tablename__ = "experiment"
+
+    id: Mapped[str] = mapped_column(String(32), primary_key=True)
+    kind: Mapped[str] = mapped_column(String(16))
+    spec_json: Mapped[str] = mapped_column(Text)
+    result_json: Mapped[str] = mapped_column(Text)
+    summary_text: Mapped[str | None] = mapped_column(String(200), nullable=True)
+    code_version: Mapped[str | None] = mapped_column(String(40), nullable=True)
+    data_version: Mapped[str | None] = mapped_column(String(40), nullable=True)
+    job_id: Mapped[str | None] = mapped_column(String(32), nullable=True)
+    created_at: Mapped[datetime] = mapped_column(DateTime)