fix: 修复代码审查发现的所有 bug

Critical 级别:
- zhipu.ts: 添加 API 响应边界检查
- DictionaryClient.tsx: 添加 entries 数组边界检查
- subtitleParser.ts: 修复 getNearestIndex 逻辑错误

High 级别:
- text-speaker/page.tsx: 修复非空断言和 ref 检查
- folder-repository.ts: 添加 user 关系 null 检查

Medium 级别:
- InFolder.tsx: 修复 throw result.message 为 throw new Error()
- localStorageOperators.ts: 返回类型改为 T | null，添加 schema 验证
- SaveList.tsx: 处理 data 可能为 null 的情况

src/app/(features)/dictionary/DictionaryClient.tsx

@@ -90,11 +90,11 @@ export function DictionaryClient({ initialFolders }: DictionaryClientProps) {
     const folderSelect = document.getElementById("folder-select") as HTMLSelectElement;
     const folderId = folderSelect?.value ? Number(folderSelect.value) : folders[0]?.id;
 
-    if (!searchResult) return;
+    if (!searchResult?.entries?.length) return;
 
-    const definition = searchResult.entries.reduce((p, e) => {
-      return { ...p, definition: p.definition + ' | ' + e.definition };
-    }).definition;
+    const definition = searchResult.entries
+      .map((e) => e.definition)
+      .join(" | ");
 
     try {
       await actionCreatePair({
@@ -102,7 +102,7 @@ export function DictionaryClient({ initialFolders }: DictionaryClientProps) {
         text2: definition,
         language1: queryLang,
         language2: definitionLang,
-        ipa1: searchResult.entries[0].ipa,
+        ipa1: searchResult.entries[0]?.ipa,
         folderId: folderId,
       });