feat(portfolio): max_pool 字段透传(model+handler+前端,解除30硬编码)

model 加 max_pool 字段(默认30,0=全市场不限);handler 用 req.max_pool 替换硬编码30;
前端加选股池上限 input + onSubmit 透传。下游 submit_portfolio→spec→argv--max-pool
链路异步化时已存在,本次只补入口。全周期验收可传 max_pool=0 对比 docker exec 旁证

sanguo_api/routes_portfolio.py

@@ -37,6 +37,7 @@ class PortfolioBacktestRequest(BaseModel):
         default="all_weather",
         description="策略: all_weather/momentum_timing/value_selection/small_cap",
     )
+    max_pool: int = Field(default=30, description="选股池上限: 0=全市场不限, N=前N只(MVP验证用)")
 
 
 @router.post("/portfolio/backtest", dependencies=[Depends(verify_token)])
@@ -48,7 +49,7 @@ async def run_portfolio_backtest(req: PortfolioBacktestRequest):
         cash=req.initial_cash,
         benchmark=req.benchmark,
         strategy=req.strategy,
-        max_pool=30,
+        max_pool=req.max_pool,
         provider_config=None,
     )
     return {"task_id": tid}