Broker usage: add reset_at (credit renewal date)

app/main.py

@@ -1193,6 +1193,7 @@ async def broker_get_usage(email: str) -> dict:
 
     balance = get_member_balance(email)
     spend = 0.0
+    reset_at = None
 
     async with httpx.AsyncClient() as client:
         # 1. Team spend + budget
@@ -1205,6 +1206,7 @@ async def broker_get_usage(email: str) -> dict:
             if t.get("team_id") == team_id:
                 balance = float(t.get("max_budget") or balance)
                 spend = float(t.get("spend") or 0.0)
+                reset_at = t.get("budget_reset_at")
                 break
 
         # 2. Per-model token/spend breakdown from spend logs (filtered by team).
@@ -1245,6 +1247,7 @@ async def broker_get_usage(email: str) -> dict:
         "spend": spend,
         "remaining": max(balance - spend, 0.0),
         "total_tokens": total_tokens,
+        "reset_at": reset_at,
         "models": model_list,
     }