学习概览日历可查看当日语法检测+跟读录音;修复跟读录音签名

- 学习概览选中某天展示:打卡任务+英语语法检测(分数)+单词跟读录音(回放)
- 修复跟读录音无法听:Safari 录音为 audio/mp4,原写死 audio/webm 致签名
  不匹配上传失败;改为按实际录音类型签名,扩展名 m4a/webm

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/app/words/word-day.tsx

@@ -36,8 +36,9 @@ function RecordBtn({ day, word }: { day: number; word: string }) {
         setBusy(true);
         stream.getTracks().forEach((t) => t.stop());
         const blob = new Blob(chunks, { type: mr.mimeType || "audio/webm" });
-        const { url, key } = await getRecUploadUrl(word);
-        await fetch(url, { method: "PUT", headers: { "Content-Type": blob.type || "audio/webm" }, body: blob });
+        const ct = blob.type || "audio/webm";
+        const { url, key } = await getRecUploadUrl(word, ct);
+        await fetch(url, { method: "PUT", headers: { "Content-Type": ct }, body: blob });
         await saveRecording(day, word, key);
         setBusy(false);
         setSaved(true);