Donate stranka: PAY by square QR s vyberom sumy

Linka Na kavu v hlavicke lobby vedie na /donate. QR sa generuje
dynamicky (balicek bysquare) pre presety 1/2/5 EUR alebo vlastnu sumu;
IBAN sa da skopirovat do schranky. Navstevy loguje existujuci
pageview beacon.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/App.tsx

@@ -9,6 +9,7 @@ import Lobby from './pages/Lobby';
 import GameTable from './pages/GameTable';
 import Auth from './pages/Auth';
 import History from './pages/History';
+import Donate from './pages/Donate';
 
 // Admin pulls in recharts — lazy-load it so players never download that chunk.
 const AdminLayout = lazy(() => import('./pages/admin/AdminLayout'));
@@ -107,6 +108,7 @@ function AppInner() {
           <Route path="/auth" element={<Auth />} />
           <Route path="/" element={<GameList />} />
           <Route path="/history" element={<History />} />
+          <Route path="/donate" element={<Donate />} />
           <Route path="/lobby/:gid" element={<Lobby />} />
           <Route path="/game/:gid" element={<GameTable />} />
           <Route path="/admin" element={<AdminLayout />}>

frontend/src/pages/Donate.tsx

@@ -0,0 +1,113 @@
+import { useMemo, useState } from 'react';
+import { useNavigate } from 'react-router-dom';
+import { QRCodeSVG } from 'qrcode.react';
+import { encode, PaymentOptions, CurrencyCode } from 'bysquare/pay';
+
+const IBAN = 'SK2583300000002803542822';
+const AMOUNTS = [1, 2, 5];
+const PAYMENT_NOTE = 'Bridzik';
+const BENEFICIARY = 'Liptak Timotej';
+
+export default function Donate() {
+  const navigate = useNavigate();
+  const [amount, setAmount] = useState(2);
+  const [custom, setCustom] = useState('');
+  const [copied, setCopied] = useState(false);
+
+  // Vlastna suma ma prednost pred presetom; akceptuje ciarku aj bodku.
+  const customParsed = parseFloat(custom.replace(',', '.'));
+  const customValid = custom !== '' && !isNaN(customParsed) && customParsed > 0;
+  const effectiveAmount = customValid ? Math.round(customParsed * 100) / 100 : amount;
+
+  const qrValue = useMemo(
+    () =>
+      encode({
+        payments: [
+          {
+            type: PaymentOptions.PaymentOrder,
+            amount: effectiveAmount,
+            currencyCode: CurrencyCode.EUR,
+            paymentNote: PAYMENT_NOTE,
+            beneficiary: { name: BENEFICIARY },
+            bankAccounts: [{ iban: IBAN }],
+          },
+        ],
+      }),
+    [effectiveAmount],
+  );
+
+  const copyIban = async () => {
+    await navigator.clipboard.writeText(IBAN);
+    setCopied(true);
+    setTimeout(() => setCopied(false), 2000);
+  };
+
+  return (
+    <div className="max-w-md mx-auto p-4 pt-8 min-h-screen">
+      <div className="flex items-center justify-between mb-6">
+        <h1 className="font-serif text-2xl text-gold">Podpor Bridžik ☕</h1>
+        <button onClick={() => navigate('/')} className="text-sm text-green-dim hover:text-gold">
+          Späť
+        </button>
+      </div>
+
+      <div className="bg-header border border-[#142018] rounded-2xl p-6 text-sm text-green-score">
+        <p className="text-green-dim mb-4">
+          Bridžik je zadarmo. Ak sa ti hra páči, dobrovoľný príspevok pomôže s prevádzkou servera a rozvojom nových funkcionalít.
+        </p>
+
+        <div className="flex gap-2 mb-2">
+          {AMOUNTS.map((a) => (
+            <button
+              key={a}
+              onClick={() => {
+                setAmount(a);
+                setCustom('');
+              }}
+              className={`flex-1 py-1.5 rounded-lg font-serif font-semibold transition-colors ${
+                !customValid && amount === a
+                  ? 'bg-gold text-table'
+                  : 'border border-gold/40 text-gold hover:bg-gold/10'
+              }`}
+            >
+              {a} €
+            </button>
+          ))}
+        </div>
+
+        <div
+          className={`flex items-center gap-2 rounded-lg border px-3 py-1.5 mb-4 transition-colors ${
+            customValid ? 'border-gold bg-gold/10' : 'border-gold/40'
+          }`}
+        >
+          <input
+            type="text"
+            inputMode="decimal"
+            placeholder="Vlastná suma"
+            value={custom}
+            onChange={(e) => setCustom(e.target.value)}
+            className="flex-1 bg-transparent outline-none text-gold placeholder-green-dim font-serif font-semibold"
+          />
+          <span className="text-gold font-serif font-semibold">€</span>
+        </div>
+
+        <div className="bg-white rounded-xl p-4 flex justify-center mb-2">
+          <QRCodeSVG value={qrValue} size={176} />
+        </div>
+        <p className="text-center text-xs text-green-dim mb-4">
+          Naskenuj QR kód bankovou aplikáciou (PAY by square)
+        </p>
+
+        <div className="flex items-center justify-between gap-2 border border-gold/20 rounded-lg px-3 py-2">
+          <span className="font-mono text-xs break-all">{IBAN}</span>
+          <button
+            onClick={copyIban}
+            className="shrink-0 text-gold hover:text-gold-bright text-xs font-semibold"
+          >
+            {copied ? 'Skopírované ✓' : 'Kopírovať'}
+          </button>
+        </div>
+      </div>
+    </div>
+  );
+}

frontend/src/pages/GameList.tsx

@@ -38,6 +38,9 @@ export default function GameList() {
           <button onClick={() => navigate('/history')} className="text-gold hover:text-gold-bright">
             História
           </button>
+          <button onClick={() => navigate('/donate')} className="text-gold hover:text-gold-bright">
+            Na kávu
+          </button>
           <button onClick={handleLogout} className="text-green-dim hover:text-gold">
             Odhlásiť
           </button>