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/ui/MoreButton.tsx

@@ -0,0 +1,37 @@
+import { MoreHorizontal } from "lucide-react";
+import { IconButton } from "./IconButton";
+import { type IconButtonSize, type IconButtonVariant } from "./buttonStyles";
+
+// The visible door to an object's ONE action list (docs/DESIGN.md "Action placement", C1): the "…"
+// that opens the same menu as a right-click, a long-press and Shift+F10, so no action is reachable
+// only by a gesture. It carries no menu of its own — `menuProps` is the list's
+// `useContextMenu().buttonProps(row)`, and `expanded` says whether THIS row's menu is the open one.
+export function MoreButton({
+  label,
+  expanded,
+  menuProps,
+  variant = "ghost",
+  size = "sm",
+  className,
+}: {
+  /** The menu's name ("Video actions"): the button's accessible name and tooltip. */
+  label: string;
+  expanded: boolean;
+  menuProps: Record<string, unknown>;
+  variant?: IconButtonVariant;
+  size?: IconButtonSize;
+  className?: string;
+}) {
+  return (
+    <IconButton
+      variant={variant}
+      size={size}
+      label={label}
+      aria-expanded={expanded}
+      className={className}
+      {...menuProps}
+    >
+      <MoreHorizontal />
+    </IconButton>
+  );
+}