feat: footer, auto-pause on no viewers, and Redsys question submissions

- Footer: add site-footer with one-liner + Cloud Host branding linking to cloudhost.es (mobile only, hidden on desktop)
- Auto-pause: game pauses automatically after AUTOPAUSE_DELAY_MS (default 60s) with no viewers connected; auto-resumes when first viewer connects; shows "Esperando espectadores…" in the UI
- Redsys: new /pregunta page lets viewers pay 1€ via Redsys to submit a fill-in question; submitted questions are used as prompts in the next round instead of AI generation; new redsys.ts implements HMAC_SHA256_V1 signing (3DES key derivation + HMAC-SHA256); notification endpoint at /api/redsys/notificacion handles server-to-server confirmation
- db.ts: questions table with createPendingQuestion / markQuestionPaid / getNextPendingQuestion / markQuestionUsed
- .env.sample: added AUTOPAUSE_DELAY_MS, PUBLIC_URL, REDSYS_* vars

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

db.ts

@@ -41,3 +41,36 @@ export function clearAllRounds() {
   db.exec("DELETE FROM rounds;");
   db.exec("DELETE FROM sqlite_sequence WHERE name = 'rounds';");
 }
+
+// ── Questions (user-submitted via Redsys) ───────────────────────────────────
+
+db.exec(`
+  CREATE TABLE IF NOT EXISTS questions (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    text TEXT NOT NULL,
+    order_id TEXT NOT NULL UNIQUE,
+    status TEXT NOT NULL DEFAULT 'pending',
+    created_at DATETIME DEFAULT CURRENT_TIMESTAMP
+  );
+`);
+
+export function createPendingQuestion(text: string, orderId: string): number {
+  const stmt = db.prepare("INSERT INTO questions (text, order_id) VALUES ($text, $orderId)");
+  const result = stmt.run({ $text: text, $orderId: orderId });
+  return result.lastInsertRowid as number;
+}
+
+export function markQuestionPaid(orderId: string): boolean {
+  const stmt = db.prepare("UPDATE questions SET status = 'paid' WHERE order_id = $orderId AND status = 'pending'");
+  const result = stmt.run({ $orderId: orderId });
+  return result.changes > 0;
+}
+
+export function getNextPendingQuestion(): { id: number; text: string; order_id: string } | null {
+  return db.query("SELECT id, text, order_id FROM questions WHERE status = 'paid' ORDER BY id ASC LIMIT 1")
+    .get() as { id: number; text: string; order_id: string } | null;
+}
+
+export function markQuestionUsed(id: number): void {
+  db.prepare("UPDATE questions SET status = 'used' WHERE id = $id").run({ $id: id });
+}