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>

frontend.tsx

@@ -621,6 +621,7 @@ function ProposeAnswer({ activeRound }: { activeRound: RoundState | null }) {
 
   const [credit, setCredit] = useState<CreditInfo | null>(null);
   const [loaded, setLoaded] = useState(false);
+  const [isAdmin, setIsAdmin] = useState(false);
   const [verifying, setVerifying] = useState(false);
   const [verifyError, setVerifyError] = useState(false);
   const [selectedTier, setSelectedTier] = useState<ProposeTierId | null>(null);
@@ -637,6 +638,10 @@ function ProposeAnswer({ activeRound }: { activeRound: RoundState | null }) {
   useEffect(() => {
     setCredit(loadCredit());
     setLoaded(true);
+    // Check if admin is logged in (cookie-based, no token needed)
+    fetch("/api/admin/status")
+      .then(r => { if (r.ok) setIsAdmin(true); })
+      .catch(() => {});
   }, []);
 
   // Clear submission state when a new round starts
@@ -704,28 +709,33 @@ function ProposeAnswer({ activeRound }: { activeRound: RoundState | null }) {
 
   async function handleSubmitAnswer(e: React.FormEvent) {
     e.preventDefault();
-    if (!credit || !activeRound) return;
+    if (!credit && !isAdmin) return;
+    if (!activeRound) return;
     setSubmitError(null);
     setSubmitting(true);
     try {
       const res = await fetch("/api/respuesta/enviar", {
         method: "POST",
         headers: { "Content-Type": "application/json" },
-        body: JSON.stringify({ text: text.trim(), token: credit.token }),
+        body: JSON.stringify({ text: text.trim(), token: credit?.token ?? "" }),
       });
       if (!res.ok) {
         if (res.status === 401) {
-          localStorage.removeItem(CREDIT_STORAGE_KEY);
-          setCredit(null);
+          if (!isAdmin) {
+            localStorage.removeItem(CREDIT_STORAGE_KEY);
+            setCredit(null);
+          }
           throw new Error("Crédito agotado o no válido.");
         }
         if (res.status === 409) throw new Error("La ronda aún no tiene pregunta activa.");
         throw new Error(await res.text() || `Error ${res.status}`);
       }
       const data = await res.json() as { ok: boolean; answersLeft: number };
-      const updated: CreditInfo = { ...credit, answersLeft: data.answersLeft };
-      localStorage.setItem(CREDIT_STORAGE_KEY, JSON.stringify(updated));
-      setCredit(updated);
+      if (credit) {
+        const updated: CreditInfo = { ...credit, answersLeft: data.answersLeft };
+        localStorage.setItem(CREDIT_STORAGE_KEY, JSON.stringify(updated));
+        setCredit(updated);
+      }
       setSubmittedFor(activeRound.num);
       setSubmittedText(text.trim());
       setText("");
@@ -742,8 +752,8 @@ function ProposeAnswer({ activeRound }: { activeRound: RoundState | null }) {
   const exhausted = credit !== null && credit.answersLeft <= 0;
   const hasPrompt = !!(activeRound?.prompt);
   const alreadySubmitted = submittedFor === activeRound?.num;
-  const canAnswer = credit && !exhausted && hasPrompt && !alreadySubmitted &&
-    (activeRound?.phase === "answering" || activeRound?.phase === "prompting");
+  const phaseOk = activeRound?.phase === "answering" || activeRound?.phase === "prompting";
+  const canAnswer = (isAdmin || (credit && !exhausted)) && hasPrompt && !alreadySubmitted && phaseOk;
 
   // Verifying payment
   if (verifying || (creditOkOrder && !credit)) {
@@ -828,6 +838,46 @@ function ProposeAnswer({ activeRound }: { activeRound: RoundState | null }) {
     );
   }
 
+  // Admin: show answer form without requiring credit
+  if (isAdmin) {
+    return (
+      <div className="propose">
+        <div className="propose__head">
+          <span className="propose__title">Responde junto a las IAs</span>
+          <span className="propose__badge" style={{ color: "var(--accent)", borderColor: "var(--accent)", background: "rgba(217,119,87,0.1)" }}>Admin</span>
+        </div>
+        {alreadySubmitted && submittedText && (
+          <p className="propose__msg propose__msg--ok">✓ Tu respuesta: &ldquo;{submittedText}&rdquo;</p>
+        )}
+        {canAnswer && (
+          <form onSubmit={handleSubmitAnswer}>
+            <div className="propose__row">
+              <textarea
+                className="propose__textarea"
+                value={text}
+                onChange={e => setText(e.target.value)}
+                placeholder="Tu respuesta más graciosa…"
+                rows={2}
+                maxLength={150}
+                autoFocus
+              />
+              <button className="propose__btn" type="submit" disabled={submitting || text.trim().length < 3}>
+                {submitting ? "…" : "Enviar"}
+              </button>
+            </div>
+            <div className="propose__hint">{text.length}/150</div>
+            {submitError && <p className="propose__msg propose__msg--error">{submitError}</p>}
+          </form>
+        )}
+        {!canAnswer && !alreadySubmitted && (
+          <p className="propose__msg" style={{ color: "var(--text-muted)" }}>
+            {!hasPrompt ? "Esperando la siguiente pregunta…" : "Ya no se aceptan respuestas para esta ronda."}
+          </p>
+        )}
+      </div>
+    );
+  }
+
   // Tier selection (purchase)
   return (
     <div className="propose">