fix: frontend URL scheme allowlist, fetch ok-check, image onerror

Add safeUrl() to gate external search-result URLs into href/src (blocks
javascript:/data:), parse the response body before the ok check in apiJson
so non-JSON error bodies surface the real status, and hide broken evidence
preview images via onerror.

web/operator-gui/app.js

@@ -123,11 +123,29 @@ async function apiJson(path, options = {}) {
 
   });
 
-  const payload = await response.json();
+  const text = await response.text();
+
+  let payload = null;
+
+  if (text) {
+
+    try {
+
+      payload = JSON.parse(text);
+
+    } catch (error) {
+
+      payload = null;
+
+    }
+
+  }
 
   if (!response.ok) {
 
-    throw new Error(payload.error || `API 요청 실패: ${response.status}`);
+    const message = (payload && payload.error) || `API 요청 실패: ${response.status}`;
+
+    throw new Error(message);
 
   }
 
@@ -523,6 +541,28 @@ function escapeHtml(value) {
 
 
 
+function safeUrl(value) {
+
+  // Defense-in-depth for URLs derived from external search results: only allow
+
+  // absolute http(s) or same-origin paths into href/src (blocks javascript:,
+
+  // data:, etc.). The server also normalizes these server-side.
+
+  const url = String(value || "").trim();
+
+  if (/^https?:\/\//i.test(url) || url.startsWith("/")) {
+
+    return url;
+
+  }
+
+  return "#";
+
+}
+
+
+
 function formatReason(reason) {
   const text = String(reason || "");
   if (!text) return "";
@@ -1719,9 +1759,9 @@ function renderEvidencePreview(evidence) {
 
   return `
 
-    <a class="evidence-preview" href="${escapeHtml(targetUrl)}" target="_blank" rel="noreferrer" aria-label="검색 이미지 열기">
+    <a class="evidence-preview" href="${escapeHtml(safeUrl(targetUrl))}" target="_blank" rel="noreferrer" aria-label="검색 이미지 열기">
 
-      <img src="${escapeHtml(previewUrl)}" alt="">
+      <img src="${escapeHtml(safeUrl(previewUrl))}" alt="" onerror="this.style.display='none'">
 
     </a>
 
@@ -1741,7 +1781,7 @@ function renderEvidenceLink(evidence) {
 
   return `
 
-    <a class="evidence-link" href="${escapeHtml(url)}" target="_blank" rel="noreferrer">
+    <a class="evidence-link" href="${escapeHtml(safeUrl(url))}" target="_blank" rel="noreferrer">
 
       ${escapeHtml(label)}
 
@@ -1937,7 +1977,7 @@ function renderCollectionCandidates() {
                 </div>
                 ${
                   candidate.sourceUrl
-                    ? `<a class="evidence-link" href="${escapeHtml(candidate.sourceUrl)}" target="_blank" rel="noreferrer">출처 열기</a>`
+                    ? `<a class="evidence-link" href="${escapeHtml(safeUrl(candidate.sourceUrl))}" target="_blank" rel="noreferrer">출처 열기</a>`
                     : ""
                 }
               </div>