Feature-Voting, Giveaways und Contribution-Heatmap

- /wunsch: Voting-Embed mit 👍, Reaction-Tracking (add/remove) in SQLite,
  Top-20-Rangliste öffentlich auf der Roadmap-Seite
- /giveaway (Admin): Preis/Dauer/Gewinnerzahl, 🎉-Teilnahme-Button (toggle),
  Minuten-Scheduler zieht Gewinner, schließt das Embed ab und pingt sie
- Contribution-Heatmap: 52-Wochen-Grid in Brand-Gelb aus dem Commit-Archiv
  (/api/heatmap) auf der Roadmap-Seite
- Setting voting_channel_id auf der Setup-Seite

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

frontend/src/pages/Roadmap.jsx

@@ -43,12 +43,53 @@ function Milestone({ m }) {
     );
 }
 
+/** GitHub-Style-Heatmap: 52 Wochen × 7 Tage */
+function Heatmap({ days }) {
+    const byDay = new Map(days.map((d) => [d.day, d.n]));
+    const max = Math.max(1, ...days.map((d) => d.n));
+    const today = new Date();
+    // Start: Montag vor ~52 Wochen
+    const start = new Date(today.getTime() - 364 * 86400000);
+    start.setDate(start.getDate() - ((start.getDay() + 6) % 7));
+
+    const weeks = [];
+    for (let w = 0; w < 53; w++) {
+        const col = [];
+        for (let d = 0; d < 7; d++) {
+            const date = new Date(start.getTime() + (w * 7 + d) * 86400000);
+            if (date > today) break;
+            const key = date.toISOString().slice(0, 10);
+            const n = byDay.get(key) ?? 0;
+            const level = n === 0 ? 0 : Math.min(4, Math.ceil((n / max) * 4));
+            col.push(
+                <span
+                    key={d}
+                    className={`hm-cell hm-${level}`}
+                    title={`${key}: ${n} Commit${n === 1 ? '' : 's'}`}
+                />
+            );
+        }
+        weeks.push(<span className="hm-week" key={w}>{col}</span>);
+    }
+    const total = days.reduce((sum, d) => sum + d.n, 0);
+    return (
+        <div className="roadmap-group">
+            <h2 className="settings-title">// Aktivität — {total} Commits in 12 Monaten</h2>
+            <div className="hm-wrap">{weeks}</div>
+        </div>
+    );
+}
+
 export default function Roadmap() {
     const [data, setData] = useState(null);
+    const [wishes, setWishes] = useState([]);
+    const [heatmap, setHeatmap] = useState(null);
     const [error, setError] = useState(false);
 
     useEffect(() => {
         apiGet('/api/roadmap').then(setData).catch(() => setError(true));
+        apiGet('/api/wishes').then((d) => setWishes(d.wishes)).catch(() => {});
+        apiGet('/api/heatmap').then((d) => setHeatmap(d.days)).catch(() => {});
         window.scrollTo(0, 0);
     }, []);
 
@@ -73,6 +114,24 @@ export default function Roadmap() {
                     <p className="notice">Noch keine Meilensteine angelegt.</p>
                 )}
 
+                {heatmap && heatmap.length > 0 && <Heatmap days={heatmap} />}
+
+                {wishes.length > 0 && (
+                    <div className="roadmap-group">
+                        <h2 className="settings-title">// Community-Wünsche</h2>
+                        {wishes.map((w, i) => (
+                            <div className="wish-row" key={`${w.created_at}-${i}`}>
+                                <span className="wish-score">👍 {w.score}</span>
+                                <span className="wish-idea">{w.idea}</span>
+                                <span className="wish-author">{w.author}</span>
+                            </div>
+                        ))}
+                        <p className="notice" style={{ padding: '.6rem 0 0' }}>
+                            Eigene Idee? Im Discord einfach <code>/wunsch</code> benutzen.
+                        </p>
+                    </div>
+                )}
+
                 {GROUPS.map(({ id, tag, empty }) => {
                     const items = (data?.milestones ?? []).filter((m) => groupOf(m) === id);
                     if (items.length === 0 && !empty) return null;