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>

src/db.js

@@ -178,6 +178,80 @@ export const listGallery = (limit, offset) => ({
     total: countGalleryStmt.get().n,
 });
 
+// Feature-Voting (/wunsch) + Giveaways
+db.exec(`
+    CREATE TABLE IF NOT EXISTS wishes (
+        message_id TEXT PRIMARY KEY,
+        author     TEXT,
+        idea       TEXT NOT NULL,
+        score      INTEGER NOT NULL DEFAULT 0,
+        created_at TEXT NOT NULL DEFAULT (datetime('now'))
+    );
+    CREATE TABLE IF NOT EXISTS giveaways (
+        message_id TEXT PRIMARY KEY,
+        channel_id TEXT NOT NULL,
+        prize      TEXT NOT NULL,
+        winners    INTEGER NOT NULL DEFAULT 1,
+        ends_at    TEXT NOT NULL,
+        ended      INTEGER NOT NULL DEFAULT 0
+    );
+    CREATE TABLE IF NOT EXISTS giveaway_entries (
+        giveaway_id TEXT NOT NULL,
+        user_id     TEXT NOT NULL,
+        PRIMARY KEY (giveaway_id, user_id)
+    );
+`);
+
+const insertWish = db.prepare('INSERT INTO wishes (message_id, author, idea) VALUES (?, ?, ?)');
+const wishScoreStmt = db.prepare('UPDATE wishes SET score = MAX(0, score + ?) WHERE message_id = ?');
+const hasWishStmt = db.prepare('SELECT 1 FROM wishes WHERE message_id = ?');
+const topWishesStmt = db.prepare(
+    'SELECT idea, author, score, created_at FROM wishes ORDER BY score DESC, created_at DESC LIMIT ?'
+);
+export const saveWish = (messageId, author, idea) => insertWish.run(messageId, author, idea);
+export const isWish = (messageId) => Boolean(hasWishStmt.get(messageId));
+export const bumpWish = (messageId, delta) => wishScoreStmt.run(delta, messageId);
+export const topWishes = (limit = 20) => topWishesStmt.all(limit);
+
+const insertGiveaway = db.prepare(`
+    INSERT INTO giveaways (message_id, channel_id, prize, winners, ends_at)
+    VALUES (@message_id, @channel_id, @prize, @winners, @ends_at)
+`);
+const dueGiveawaysStmt = db.prepare(
+    `SELECT * FROM giveaways WHERE ended = 0 AND ends_at <= datetime('now')`
+);
+const endGiveawayStmt = db.prepare('UPDATE giveaways SET ended = 1 WHERE message_id = ?');
+const giveawayStmt = db.prepare('SELECT * FROM giveaways WHERE message_id = ?');
+const toggleEntryInsert = db.prepare(
+    'INSERT OR IGNORE INTO giveaway_entries (giveaway_id, user_id) VALUES (?, ?)'
+);
+const toggleEntryDelete = db.prepare(
+    'DELETE FROM giveaway_entries WHERE giveaway_id = ? AND user_id = ?'
+);
+const entriesStmt = db.prepare('SELECT user_id FROM giveaway_entries WHERE giveaway_id = ?');
+export const saveGiveaway = (g) => insertGiveaway.run(g);
+export const getGiveaway = (id) => giveawayStmt.get(id) ?? null;
+export const dueGiveaways = () => dueGiveawaysStmt.all();
+export const markGiveawayEnded = (id) => endGiveawayStmt.run(id);
+export const giveawayEntries = (id) => entriesStmt.all(id).map((r) => r.user_id);
+/** Teilnahme togglen — true = jetzt drin, false = ausgetragen */
+export function toggleGiveawayEntry(giveawayId, userId) {
+    if (toggleEntryInsert.run(giveawayId, userId).changes > 0) return true;
+    toggleEntryDelete.run(giveawayId, userId);
+    return false;
+}
+
+/** Commits pro Tag der letzten 365 Tage (Contribution-Heatmap) */
+export function commitHeatmap() {
+    return db
+        .prepare(`
+            SELECT date(committed_at) AS day, count(*) AS n
+            FROM commits WHERE committed_at >= datetime('now', '-365 days')
+            GROUP BY day
+        `)
+        .all();
+}
+
 // Modmail: DM-Konversationen ↔ Staff-Threads
 db.exec(`
     CREATE TABLE IF NOT EXISTS modmail (