Unify error handling and HTTP statuses

Signed-off-by: Sean Du <do4suki@gmail.com>

internal/handler/api/reward/list.go

@@ -2,6 +2,7 @@ package reward
 
 import (
 	rewardapischema "honoka-chan/internal/schema/api/reward"
+	"net/http"
 	"time"
 )
 
@@ -13,7 +14,7 @@ func rewardList() (res any, err error) {
 			Order:     0,
 			Items:     []any{},
 		},
-		Status:     200,
+		Status:     http.StatusOK,
 		CommandNum: false,
 		TimeStamp:  time.Now().Unix(),
 	}