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>

frontend.tsx

@@ -41,6 +41,7 @@ type GameState = {
   viewerScores: Record<string, number>;
   done: boolean;
   isPaused: boolean;
+  autoPaused?: boolean;
   generation: number;
 };
 type StateMessage = {
@@ -616,7 +617,7 @@ function App() {
                   className="viewer-pill"
                   style={{ color: "var(--text-muted)", borderColor: "var(--border)" }}
                 >
-                  En pausa
+                  {state.autoPaused ? "Esperando espectadores…" : "En pausa"}
                 </div>
               )}
               <div className="viewer-pill" aria-live="polite">
@@ -654,6 +655,21 @@ function App() {
 
         <Standings scores={state.scores} viewerScores={state.viewerScores ?? {}} activeRound={state.active} />
       </div>
+      <footer className="site-footer">
+        <p>IAs compiten respondiendo preguntas absurdas — los jueces votan, tú también puedes.</p>
+        <p>
+          por{" "}
+          <a
+            href="https://cloudhost.es"
+            target="_blank"
+            rel="noopener noreferrer"
+            className="site-footer__link"
+          >
+            Cloud Host
+          </a>
+          {" "}— La web simplificada, la nube gestionada
+        </p>
+      </footer>
     </div>
   );
 }