securite: #87 T5a supprime 16 handlers inline au profit de listeners (CSP inchangee)

frontend/js/auth.js

@@ -1305,8 +1305,7 @@ async function _startMfaSetup() {
     // secret when the backend has no QR generator available.
     const qrImg = data.qr_data_url
       ? `<img id="mfa-qr-img" alt="QR Code" class="mfa-qr-code-img"
-              src="${data.qr_data_url}"
-              onerror="this.style.display='none';document.getElementById('mfa-qr-fallback').style.display='block';">`
+              src="${data.qr_data_url}">`
       : "";
     const fallbackStyle = data.qr_data_url ? "display:none" : "";
     flowArea.innerHTML = `
@@ -1335,6 +1334,17 @@ async function _startMfaSetup() {
       codeInput.value = codeInput.value.replace(/[^0-9]/g, "");
     });
 
+    // QR fallback (#87, ex-onerror inline) : si l'image ne charge pas,
+    // afficher la saisie manuelle du secret.
+    const qrImgEl = document.getElementById("mfa-qr-img");
+    if (qrImgEl) {
+      qrImgEl.addEventListener("error", () => {
+        qrImgEl.style.display = "none";
+        const fallback = document.getElementById("mfa-qr-fallback");
+        if (fallback) fallback.style.display = "block";
+      });
+    }
+
     document.getElementById("mfa-confirm-btn").addEventListener("click", async () => {
       const code = codeInput.value.trim();
       if (code.length !== 6) return;