Economy: free vs paid games + buy-coins page; friends remove confirmation

- Coins only matter for ranked: free games (vs computer / private friend rooms)
  cost nothing; random ranked requires an entry (stake), gated by balance →
  routes to buy-coins when short
- Buy Coins page (CoinPack/getCoinPacks/buyCoins; mock credits now, real
  Zarinpal/IDPay TODO); TopBar coins → buy; lobby create-room is Free
- Friends: removed instant red ✕ delete; UserMinus → inline confirm before remove

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

src/components/online/TopBar.tsx

@@ -55,12 +55,17 @@ export function TopBar() {
         >
           <Gift className="size-4 text-gold-400" />
         </button>
-        <div className="glass rounded-full px-3 py-1.5 flex items-center gap-1.5">
+        <button
+          onClick={() => go("buycoins")}
+          className="glass rounded-full px-3 py-1.5 flex items-center gap-1.5 hover:bg-navy-800/80 transition"
+          title={t("buy.title")}
+        >
           <Coins className="size-4 text-gold-400" />
           <span className="text-sm font-bold text-cream tabular-nums">
             {profile.coins.toLocaleString()}
           </span>
-        </div>
+          <span className="text-gold-400 text-sm leading-none font-bold">+</span>
+        </button>
       </div>
     </div>
   );