feat(design): a video's one action list (C1) — the card's "…", the menu holds the rest (E28 S3e1)

- useContextMenu gains buttonProps (a row's visible "…" opens the same menu under the button; a
  second press closes it) and anchor (the element the menu came from, for a panel a row opens).
- ui/MoreButton; ActionMenu rows can run inGesture (a clipboard write inside the click, Safari).
- useVideoActions: one builder for a video's menu (play / restart, channel, watched, save, add to
  playlist, download, details, copy title / link, hide, reset, pin), composed by the feed and by
  Home's rails; the playlists and details panels open anchored beside the card (VideoFollowUp).
- The card keeps watched / save / add to playlist and the "…": on the picture on hover (the
  duration steps aside), in the rows' action column; on touch only a 44px "…" beside the title.
  Download, hide, reset and the hover info card leave the card.
- The title is selectable: a click ending a selection neither plays nor follows the link.
- DESIGN.md: how C1 is built + the log row.

frontend/src/components/VideoMenu.tsx

@@ -0,0 +1,30 @@
+import { useTranslation } from "react-i18next";
+import { type Video } from "../lib/api";
+import { ContextMenu } from "./ui/ContextMenu";
+import { type ContextMenuController } from "./ui/useContextMenu";
+import { useVideoActions, type VideoActionHandlers } from "./useVideoActions";
+
+/** A video list's one menu (the feed grid and a channel page): every trigger — right-click,
+ *  long-press, Shift+F10 and each card's "…" — opens it with the video's whole action list. Render
+ *  ONE per list, outside the cards (see `ui/ContextMenu`). */
+export function VideoMenu({
+  menu,
+  handlers,
+}: {
+  menu: ContextMenuController<Video>;
+  handlers: VideoActionHandlers;
+}) {
+  const { t } = useTranslation();
+  const actions = useVideoActions(handlers, menu.open);
+  const v = menu.target;
+  return (
+    <>
+      <ContextMenu
+        menu={menu}
+        ariaLabel={t("card.menu.label")}
+        items={v ? actions.items(v, menu.anchor) : []}
+      />
+      {actions.panel}
+    </>
+  );
+}