feat: rank change toast + streak milestone icons

Toast notification on rank change (up/down).
Streak display with milestones: 🔥 at 3, 🔥🔥 at 10, ⚡ at 20.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/App.tsx

@@ -7,6 +7,8 @@ import LeaderboardPage from './pages/LeaderboardPage';
 import ProfilePage from './pages/ProfilePage';
 import AdminPage from './pages/AdminPage';
 import BottomNav from './components/BottomNav';
+import Toast from './components/Toast';
+import { useRankChange } from './hooks/useRankChange';
 import styles from './App.module.css';
 
 const IS_DEV = import.meta.env.DEV || import.meta.env.VITE_TEST_MODE === 'true';
@@ -28,6 +30,7 @@ function getInitialTheme(): Theme {
 
 export default function App() {
   const [theme, setTheme] = useState<Theme>(getInitialTheme);
+  const { message: rankMsg, dismiss: dismissRank } = useRankChange();
   const [devUser, setDevUser] = useState(1);
   const [devMatches, setDevMatches] = useState<any[]>([]);
   const [refreshKey, setRefreshKey] = useState(0);
@@ -115,6 +118,7 @@ export default function App() {
         </Routes>
       </main>
 
+      {rankMsg && <Toast message={rankMsg} onDismiss={dismissRank} />}
       <BottomNav />
 
       {IS_DEV && DevPanel && (

frontend/src/components/Toast.module.css

@@ -0,0 +1,25 @@
+.toast {
+  position: fixed;
+  top: 16px;
+  left: 50%;
+  transform: translateX(-50%);
+  background: color-mix(in srgb, var(--surface-high) 95%, transparent);
+  backdrop-filter: blur(12px);
+  -webkit-backdrop-filter: blur(12px);
+  color: var(--text-primary);
+  padding: 12px 20px;
+  border-radius: var(--radius-md);
+  font-size: 0.9rem;
+  font-weight: 500;
+  z-index: 300;
+  cursor: pointer;
+  animation: slideDown 0.3s ease;
+  border: 1px solid rgba(75, 183, 248, 0.15);
+  max-width: 90%;
+  text-align: center;
+}
+
+@keyframes slideDown {
+  from { transform: translateX(-50%) translateY(-100%); opacity: 0; }
+  to { transform: translateX(-50%) translateY(0); opacity: 1; }
+}

frontend/src/components/Toast.tsx

@@ -0,0 +1,21 @@
+import { useEffect } from 'react';
+import styles from './Toast.module.css';
+
+interface Props {
+  message: string;
+  onDismiss: () => void;
+  duration?: number;
+}
+
+export default function Toast({ message, onDismiss, duration = 5000 }: Props) {
+  useEffect(() => {
+    const timer = setTimeout(onDismiss, duration);
+    return () => clearTimeout(timer);
+  }, [onDismiss, duration]);
+
+  return (
+    <div className={styles.toast} onClick={onDismiss}>
+      {message}
+    </div>
+  );
+}

frontend/src/hooks/useRankChange.ts

@@ -0,0 +1,26 @@
+import { useState, useEffect } from 'react';
+import { api } from '../api/client';
+
+const RANK_KEY = 'tippspiel_last_rank';
+
+export function useRankChange() {
+  const [message, setMessage] = useState<string | null>(null);
+
+  useEffect(() => {
+    api.getMyStats().then(stats => {
+      if (!stats.rank) return;
+      const lastRank = parseInt(localStorage.getItem(RANK_KEY) || '0');
+      if (lastRank > 0 && lastRank !== stats.rank) {
+        if (stats.rank < lastRank) {
+          setMessage(`⬆️ Du bist auf Platz ${stats.rank} aufgestiegen!`);
+        } else {
+          setMessage(`⬇️ Du bist auf Platz ${stats.rank} gerutscht — hol dir die Punkte zurück!`);
+        }
+      }
+      localStorage.setItem(RANK_KEY, String(stats.rank));
+    }).catch(() => {});
+  }, []);
+
+  function dismiss() { setMessage(null); }
+  return { message, dismiss };
+}

frontend/src/pages/DashboardPage.tsx

@@ -7,6 +7,14 @@ interface Props {
   devUser?: number;
 }
 
+function formatStreak(streak: number): string {
+  if (streak >= 20) return `⚡${streak}`;
+  if (streak >= 10) return `🔥🔥${streak}`;
+  if (streak >= 3) return `🔥${streak}`;
+  if (streak > 0) return String(streak);
+  return '0';
+}
+
 function formatCountdown(minutes: number): string {
   if (minutes < 60) return `in ${minutes} Min`;
   if (minutes < 60 * 24) return `in ${Math.floor(minutes / 60)}h`;
@@ -108,9 +116,7 @@ export default function DashboardPage(_props: Props) {
           <span className={styles.statLabel}>Punkte</span>
         </div>
         <div className={styles.statTile}>
-          <span className={styles.statValue}>
-            {stats.streak > 0 ? `${stats.streak} 🔥` : stats.streak}
-          </span>
+          <span className={styles.statValue}>{formatStreak(stats.streak)}</span>
           <span className={styles.statLabel}>Streak</span>
         </div>
       </div>