Shop: every item is coin-priced; level/rank/achievement only gate the purchase

No more earned-only (rank/wins) cosmetics — every avatar, card back/front,
reaction & sticker pack now has a coin price. Rank/wins/achievement become
purchase requirements (coin · coin+rank · coin+rank+achievement), enforced
client (mock + ShopScreen lock label) and server (ProfileService.ItemGate,
keyed by kind:id). Ownership = default + purchased only.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/components/screens/ShopScreen.tsx

@@ -101,6 +101,11 @@ export function ShopScreen() {
   const lockLabel = (item: ShopItem): string | null => {
     if (item.reqLevel && profile.level < item.reqLevel) return `${t("shop.reqLevel")} ${item.reqLevel}`;
     if (item.reqRating && profile.rating < item.reqRating) return `${t("shop.reqRating")} ${item.reqRating}`;
+    if (item.reqAchievement && !(profile.unlocked ?? []).includes(item.reqAchievement)) {
+      const ach = achievementById(item.reqAchievement);
+      const name = ach ? (locale === "fa" ? ach.nameFa : ach.nameEn) : item.reqAchievement;
+      return `${t("shop.reqAchv")} ${name}`;
+    }
     return null;
   };