Add modal URL router (#modal=name&tab=key) (#3924)

## Description

Adds a modal URL router so modals can be opened, deep-linked, and
bookmarked via the hash. URLs of the form `#modal=<name>&tab=<key>&...`
open the named modal and pass remaining keys as args to `onOpen`. The
reverse direction also syncs: opening a modal via the UI updates the
URL, closing it clears the hash, and switching tabs updates `&tab=`.

Builds on the BaseModal refactor from #3923.

### What's new

**`ModalRouter.ts`** — small registry + two-way sync helper.
- `register(name, { tag, pageId? })` declares a modal as router-managed
- `routeFromHash()` parses `#modal=...` and dispatches to
`modal.open(args)`
- `syncOpened/syncClosed/syncTab` push state back into the URL via
`history.replaceState` (no history entries)
- A `routingFromUrl` flag prevents URL→modal→URL feedback loops
- Unknown modal names silently strip the hash

**`BaseModal`** — opt-in URL sync via a `routerName` property.
- When set, BaseModal calls into
`modalRouter.syncOpened/syncClosed/syncTab` from `open` / `close` /
`setActiveTab`
- Modals that own their own URL state (lobby modals) just leave
`routerName` undefined

**`Main.ts`** — registers all routable modals and wires the router.
- `handleUrl()`: adds a `modalRouter.routeFromHash()` branch after the
path-based lobby join
- `onHashUpdate`: when the hash is router-managed, routes via the router
instead of tearing down lobby state

### Routable modals

13 inline modals: store, settings, leaderboard, clan, account, help,
news, language, single-player, ranked, troubleshooting,
territory-patterns, flag-input.

Excluded by design: join-lobby, host-lobby (own URL state via
`/game/<id>`), matchmaking (no URL state).

### Example uses

- Deep link to store flags tab: `/#modal=store&tab=flags`
- Settings keybinds tab: `/#modal=settings&tab=keybinds`
- Cosmetics.ts now redirects to `#modal=store&tab=packs` when a
hard-currency purchase fails for insufficient plutonium (after the
alert), so users can top up directly

### URL behavior

- `replaceState` everywhere — no history entries added when modals open
/ close / switch tabs
- Browser back/forward still works for the existing path-based game flow
- `hashchange` events are router-aware so external hash changes (back
button, manual edit) correctly switch between routed modals without
tearing down lobby state

## Please complete the following:

- [x] I have added screenshots for all UI updates _(no visual changes;
smoke-tested in dev)_
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file _(no new user-visible strings)_
- [ ] I have added relevant tests to the test directory _(no test
coverage; manually tested URL load, UI open, tab switch, close,
hashchange, insufficient-plutonium redirect)_
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

DISCORD_USERNAME

src/client/Main.ts

@@ -43,6 +43,7 @@ import { initLayout } from "./Layout";
 import "./LeaderboardModal";
 import "./Matchmaking";
 import { MatchmakingModal } from "./Matchmaking";
+import { modalRouter } from "./ModalRouter";
 import { initNavigation } from "./Navigation";
 import "./NewsModal";
 import "./PatternInput";
@@ -268,6 +269,50 @@ class Client {
 
   async initialize(): Promise<void> {
     crazyGamesSDK.maybeInit();
+
+    // Register modals with the URL router. Lobby modals (join/host) and
+    // matchmaking are intentionally omitted — they own their own URL state
+    // (path-based) or none at all.
+    modalRouter.register("store", {
+      tag: "store-modal",
+      pageId: "page-item-store",
+    });
+    modalRouter.register("settings", {
+      tag: "user-setting",
+      pageId: "page-settings",
+    });
+    modalRouter.register("leaderboard", {
+      tag: "leaderboard-modal",
+      pageId: "page-leaderboard",
+    });
+    modalRouter.register("clan", { tag: "clan-modal", pageId: "page-clan" });
+    modalRouter.register("account", {
+      tag: "account-modal",
+      pageId: "page-account",
+    });
+    modalRouter.register("help", { tag: "help-modal", pageId: "page-help" });
+    modalRouter.register("news", { tag: "news-modal", pageId: "page-news" });
+    modalRouter.register("language", {
+      tag: "language-modal",
+      pageId: "page-language",
+    });
+    modalRouter.register("single-player", {
+      tag: "single-player-modal",
+      pageId: "page-single-player",
+    });
+    modalRouter.register("ranked", {
+      tag: "ranked-modal",
+      pageId: "page-ranked",
+    });
+    modalRouter.register("troubleshooting", {
+      tag: "troubleshooting-modal",
+      pageId: "page-troubleshooting",
+    });
+    modalRouter.register("territory-patterns", {
+      tag: "territory-patterns-modal",
+    });
+    modalRouter.register("flag-input", { tag: "flag-input-modal" });
+
     // Prefetch turnstile token so it is available when
     // the user joins a lobby.
     this.turnstileTokenPromise = getTurnstileToken();
@@ -525,6 +570,13 @@ class Client {
     }
 
     const onHashUpdate = () => {
+      // Router-managed hash changes (#modal=...) are handled by the router
+      // syncing in/out; we don't need to tear down the lobby state for them.
+      if (modalRouter.isHashRouted()) {
+        modalRouter.routeFromHash();
+        return;
+      }
+
       // Reset the UI to its initial state
       this.joinModal?.close();
 
@@ -725,6 +777,9 @@ class Client {
       console.log(`joining lobby ${lobbyId}`);
       return;
     }
+    if (modalRouter.routeFromHash()) {
+      return;
+    }
     if (decodedHash.startsWith("#affiliate=")) {
       const affiliateCode = decodedHash.replace("#affiliate=", "");
       strip();