feat: T1.7 投后报告导出 + T1.8 docker-compose.dev.yml + T0.4 补全

- 后端：reports_export 路由（summary 聚合 + JSON 导出）
- 测试：3 个导出测试，总计 67 passed
- docker-compose.dev.yml：开发覆盖（源码挂载 + hot reload + debugpy）
- 前端 14 路由构建成功

backend/app/main.py

@@ -15,6 +15,7 @@ from app.routers.companies import router as companies_router
 from app.routers.copilot import router as copilot_router
 from app.routers.dashboard import router as dashboard_router
 from app.routers.reports import router as reports_router
+from app.routers.reports_export import router as reports_export_router
 from app.routers.risks import router as risks_router
 from app.schemas.common import error
 
@@ -77,3 +78,4 @@ app.include_router(reports_router, prefix="/api/v1")
 app.include_router(dashboard_router, prefix="/api/v1")
 app.include_router(risks_router, prefix="/api/v1")
 app.include_router(copilot_router, prefix="/api/v1")
+app.include_router(reports_export_router, prefix="/api/v1")