feat(e24): reach the Home surface — the landing toggle, a palette command, Shift+W

S4's reachability half. Home already led the nav order; what was missing was every
way IN other than the rail.

- Settings → Appearance → Startup: "Start on Home", the documented escape hatch for
  the landing override. Deliberately still localStorage and not a server pref —
  `loadInitialPage` answers before /api/me lands, and a landing module decided after
  the first paint is a visible jump. Its two stored values are now ONE exported
  constant, so the writer and the boot-time reader cannot drift on a magic string.
- The command palette gets "Meglepetés" / "Surprise me": it navigates to Home and
  rerolls the hero on arrival. No second "Mit nézzek?" row beside it — the Home
  module row already matches that phrase through its descriptive title.
- A global Shift+W jumps to Home. A chord, not a bare `w`: the Plex player binds bare
  letters and `w` sits on `s`, so a blind reach for the subtitle key would have thrown
  a viewer out of the film.

The palette's request crosses a lazy module boundary, so it is a token that waits
(lib/homeIntent) rather than an event fired into an empty room. Browser-measured:
taken with a compare-and-clear, because StrictMode's double-invoked mount effect
otherwise rerolled twice and landed on the page two picks deep.

HU/EN parity kept; UAT on localdev in both languages, including the empty shelf.

frontend/src/components/ui/KeyboardHelp.dom.test.tsx

@@ -27,9 +27,9 @@ afterEach(() => {
   closeKeyboardHelp();
 });
 
-/** App's job: it binds the `global` scope (h / Mod+K) once for the whole tree. */
+/** App's job: it binds the `global` scope (h / Mod+K / Shift+W) once for the whole tree. */
 function Host({ children }: { children?: React.ReactNode }) {
-  useGlobalKeymap();
+  useGlobalKeymap(true, () => {});
   return (
     <>
       {children}
@@ -83,13 +83,13 @@ describe("KeyboardHelp", () => {
     const rows = descriptions();
     // A plexPlayer row first, the app-wide rows last — the reading order the reader wants.
     expect(rows[0]).toBe("keys.playPause");
-    expect(rows.slice(-2)).toEqual(["keys.palette", "keys.help"]);
+    expect(rows.slice(-3)).toEqual(["keys.palette", "keys.help", "keys.home"]);
   });
 
   it("lists only the app-wide keys when no surface is registered", () => {
     render(<Host />);
     pressH();
-    expect(descriptions()).toEqual(["keys.palette", "keys.help"]);
+    expect(descriptions()).toEqual(["keys.palette", "keys.help", "keys.home"]);
   });
 
   // The context menu is NOT app-wide: it has its own scope, registered by `useContextMenu`, so the