fix(api): accept short universe names in alpha list endpoint

Normalize csi300/sp500/btc-usdt to canonical names before validation
in GET /alpha/list, matching the behavior of the bench form endpoint.

Signed-off-by: liucaiwen <liucaiwenseven@163.com>

Author: lcwSeven

agent/src/api/alpha_routes.py

@@ -282,6 +282,9 @@ async def list_alphas(
                 status_code=400,
                 detail=f"unknown theme {theme!r}; expected one of {sorted(_VALID_THEMES)}",
             )
+        if universe is not None:
+            _ALIAS = {"csi300": "equity_cn", "sp500": "equity_us", "btc-usdt": "crypto"}
+            universe = _ALIAS.get(universe, universe)
         if universe is not None and universe not in _VALID_UNIVERSES:
             raise HTTPException(
                 status_code=400,