Add crown cosmetic type (#4618)

## What

Adds **crowns** as a new cosmetic category, wired end-to-end like
flags/skins, plus a Crowns tab in the lobby cosmetics modal (#4617).

Catalog shape in cosmetics.json:

```json
"crowns": {
  "gold_crown": {
    "name": "gold_crown",
    "url": "...",
    "affiliateCode": null,
    "product": null,
    "priceHard": 5,
    "artist": "...",
    "rarity": "common"
  }
}
```

## Changes

- **Core**: `CrownSchema` + optional `crowns` record in
`CosmeticsSchema`; `crownName` in `PlayerCosmeticRefs`; resolved `crown:
{ name, url }` in `PlayerCosmetics`
- **Server**: `isCrownAllowed` in the privilege checker — requires a
`crown:*` or `crown:<name>` flare, resolves the ref to the catalog URL
- **Client**: crown selection persisted under the `crown` localStorage
key (stale/unowned selections self-clear), `crownRelationship` +
resolve/refs wiring, `"crown"` purchase type, Crowns tab in the store,
and a Crowns tab in the cosmetics modal (owned crowns + Default tile;
selecting persists and keeps the modal open)
- **i18n**: `store.crowns`, `store.no_crowns`
- Tests for schema parsing, privilege checks, and cosmetic resolution

## Not in this PR

- In-game rendering of `player.cosmetics.crown` (name pass /
leaderboards / player panel)
- API-side support (`/shop/purchase` accepting `cosmeticType: "crown"`,
granting `crown:<name>` flares, serving `crowns` in cosmetics.json)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

src/core/game/UserSettings.ts

@@ -54,6 +54,7 @@ export const USER_SETTINGS_CHANGED_EVENT = "event:user-settings-changed";
  */
 export const PATTERN_KEY = "territoryPattern";
 export const FLAG_KEY = "flag";
+export const CROWN_KEY = "crown";
 export const COLOR_KEY = "settings.territoryColor";
 export const PERFORMANCE_OVERLAY_KEY = "settings.performanceOverlay";
 export const KEYBINDS_KEY = "settings.keybinds";
@@ -301,6 +302,19 @@ export class UserSettings {
     return data.startsWith(skinPrefix) ? data.slice(skinPrefix.length) : null;
   }
 
+  /** Returns the selected crown name, or null if none is selected. */
+  getSelectedCrownName(): string | null {
+    return this.getCached(CROWN_KEY);
+  }
+
+  setSelectedCrownName(name: string | undefined): void {
+    if (name === undefined) {
+      this.removeCached(CROWN_KEY);
+    } else {
+      this.setCached(CROWN_KEY, name);
+    }
+  }
+
   getFlag(): string | null {
     let flag = this.getCached(FLAG_KEY);
     if (!flag) return null;