fix(admin-web/tracking): guard optional citations array on platform

部分平台返回的快照里没有 citations 数组，原代码直接 platform.citations[i]
会在内联引文渲染处抛 TypeError。改用可选链兜底空值。

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/admin-web/src/views/TrackingQuestionDetailView.vue

@@ -681,7 +681,7 @@ function buildInlineCitationMarker(
     return "";
   }
 
-  const hasCitation = Boolean(platform?.citations[sourceGroupIndex - 1]);
+  const hasCitation = Boolean(platform?.citations?.[sourceGroupIndex - 1]);
   const className = hasCitation
     ? "tracking-inline-citation"
     : "tracking-inline-citation tracking-inline-citation--muted";
@@ -934,7 +934,7 @@ function analyzeInlineContentCitations(
       return left[0] - right[0];
     })
     .flatMap(([sourceGroupIndex, citationCount]) => {
-      const citation = platform?.citations[sourceGroupIndex - 1] ?? null;
+      const citation = platform?.citations?.[sourceGroupIndex - 1] ?? null;
       const citedURL = citation?.cited_url?.trim() ?? "";
       if (!citedURL) {
         return [];