fix: 统一管理后台 401 与加载失败处理

internal/admin/login.go

@@ -4,6 +4,7 @@ import (
 	"database/sql"
 	"errors"
 	"net/http"
+	"unicode/utf8"
 
 	"git.asio.asia/nixevol/NixMsg/internal/auth"
 	"git.asio.asia/nixevol/NixMsg/internal/httpx"
@@ -127,7 +128,7 @@ func (h *Handler) handlePassword(w http.ResponseWriter, r *http.Request) {
 		writeDecodeError(w, err)
 		return
 	}
-	if len(req.NewPassword) < minPasswordLen {
+	if utf8.RuneCountInString(req.NewPassword) < minPasswordLen {
 		h.audit(actorString(p), "password_change", "", "bad_request", ip)
 		httpx.WriteError(w, http.StatusBadRequest, "bad_request", "新密码至少 12 位")
 		return