feat: admin can answer questions without paying for testing

- Server: /api/respuesta/enviar checks admin cookie; if authorized,
  bypasses credit check and stores answer via insertAdminAnswer()
- DB: insertAdminAnswer() inserts directly into user_answers with
  username='Admin', skipping the credit budget entirely
- Frontend: ProposeAnswer checks /api/admin/status on mount; if admin
  is logged in, shows the answer form directly (orange Admin badge)
  instead of the payment tier selection

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

server.ts

@@ -7,7 +7,8 @@ import broadcastHtml from "./broadcast.html";
 import preguntaHtml from "./pregunta.html";
 import {
   clearAllRounds, getRounds, getAllRounds,
-  createPendingCredit, activateCredit, getCreditByOrder, submitUserAnswer,
+  createPendingCredit, activateCredit, getCreditByOrder,
+  submitUserAnswer, insertAdminAnswer,
   getPlayerScores,
 } from "./db.ts";
 import { buildPaymentForm, verifyNotification, decodeParams, isPaymentApproved } from "./redsys.ts";
@@ -706,7 +707,9 @@ const server = Bun.serve<WsData>({
         return new Response("Invalid JSON body", { status: 400 });
       }
 
-      if (!token) {
+      const adminMode = isAdminAuthorized(req, url);
+
+      if (!token && !adminMode) {
         return new Response("Token requerido", { status: 401 });
       }
       if (text.length < 3 || text.length > 150) {
@@ -718,17 +721,28 @@ const server = Bun.serve<WsData>({
         return new Response("No hay ronda activa", { status: 409 });
       }
 
-      const result = submitUserAnswer(token, round.num, text);
-      if (!result) {
-        return new Response("Crédito no válido o sin respuestas disponibles", { status: 401 });
+      let username: string;
+      let answersLeft: number;
+
+      if (adminMode) {
+        username = "Admin";
+        insertAdminAnswer(round.num, text, username);
+        answersLeft = 999;
+      } else {
+        const result = submitUserAnswer(token, round.num, text);
+        if (!result) {
+          return new Response("Crédito no válido o sin respuestas disponibles", { status: 401 });
+        }
+        username = result.username;
+        answersLeft = result.answersLeft;
       }
 
       // Add to live round state and broadcast
-      round.userAnswers = [...(round.userAnswers ?? []), { username: result.username, text }];
+      round.userAnswers = [...(round.userAnswers ?? []), { username, text }];
       broadcast();
 
-      log("INFO", "respuesta", "User answer submitted", { username: result.username, round: round.num, ip });
-      return new Response(JSON.stringify({ ok: true, answersLeft: result.answersLeft }), {
+      log("INFO", "respuesta", "Answer submitted", { username, round: round.num, admin: adminMode, ip });
+      return new Response(JSON.stringify({ ok: true, answersLeft }), {
         status: 200,
         headers: { "Content-Type": "application/json", "Cache-Control": "no-store" },
       });