refactor: item 29 cleanup

F16 F17 F18 F19 F20 F21: import polling backs off and pauses in a hidden tab, one date format module, fake timers in the import tests, error codes instead of raw messages, one safe storage wrapper, dead code.

src/pages/GameLibrary.jsx

@@ -56,7 +56,6 @@ export default function GameLibrary() {
     const listStatus = hiddenOnly ? null : status;
     const listShortOnly = !hiddenOnly && shortOnly;
     const filtered = Boolean(listStatus || q.trim() || listShortOnly || hiddenOnly);
-    const librarySearch = searchParams.toString();
     const [search, setSearch] = useState(q);
     const [adding, setAdding] = useState(false);
     // Starts true until /games-count answers, so a Steam user does not see the sync controls vanish and come back.
@@ -285,7 +284,6 @@ export default function GameLibrary() {
                             <li key={g.appid}>
                                 <Link
                                     to={`/library/${g.appid}`}
-                                    state={{librarySearch}}
                                     className="group flex items-center gap-3 sm:gap-4 px-4 sm:px-5 py-3 transition-colors hover:bg-muted/50"
                                 >
                                     <GameCover appid={g.appid} imageUrl={g.imageUrl} className="w-16 sm:w-24 shrink-0"/>