refactor(design): one drawn check for every checkable row that cannot be an input (E28 S3e3b)

ui/MenuCheck: a box filled with the accent for a set (a minus for a group
only partly in), a bare tick for one choice, in the row's leading slot.
Replaces seven hand-drawn marks: three box sizes, a tinted box, a cross
for "on" in the table filter, a trailing tick in the language menu.

frontend/src/components/ui/tableHeader.tsx

@@ -1,6 +1,7 @@
 import { useRef, useState, type ReactNode } from "react";
 import { useTranslation } from "react-i18next";
-import { ArrowDown, ArrowUp, ListFilter, X } from "lucide-react";
+import { ArrowDown, ArrowUp, ListFilter } from "lucide-react";
+import { MenuCheck } from "./MenuCheck";
 import { PopoverItem, PopoverSurface } from "./AnchoredPopover";
 import { useAnchoredPopover } from "./anchoredPopoverHooks";
 import { useScrollFade } from "../../lib/useScrollFade";
@@ -158,13 +159,7 @@ function FilterFunnel<T>({
                     on ? "text-fg" : "text-muted"
                   }`}
                 >
-                  <span
-                    className={`w-3.5 h-3.5 rounded border flex items-center justify-center ${
-                      on ? "bg-accent border-accent text-accent-fg" : "border-border"
-                    }`}
-                  >
-                    {on && <X className="w-2.5 h-2.5" />}
-                  </span>
+                  <MenuCheck kind="many" on={on} />
                   {o.label}
                 </PopoverItem>
               );