feat: fix TypeScript errors and improve code quality

frontend/src/components/EpisodePlayer.tsx

@@ -13,6 +13,7 @@ export default function EpisodePlayer() {
   const [selectedEpisode, setSelectedEpisode] = useState<Episode | null>(null);
   const [audioUrl, setAudioUrl] = useState<string | null>(null);
   const [loading, setLoading] = useState(true);
+  const [isPlaying, setIsPlaying] = useState(false);
   const [error, setError] = useState<string | null>(null);
 
   useEffect(() => {

server.ts

@@ -70,7 +70,7 @@ app.get("/assets/*", async (c) => {
       : filePath.endsWith(".css")
       ? "text/css"
       : "application/octet-stream";
-    const blob = await file.blob();
+    const blob = await file.arrayBuffer();
     return c.body(blob, 200, { "Content-Type": contentType });
   }
   return c.notFound();

services/tts.ts

@@ -1,6 +1,5 @@
 import fs from "fs";
 import path from "path";
-import fetch from "node-fetch";
 
 // VOICEVOX APIの設定
 const VOICEVOX_HOST = "http://localhost:50021";
@@ -54,7 +53,8 @@ export async function generateTTS(
     throw new Error("VOICEVOX 音声合成に失敗しました");
   }
 
-  const audioBuffer = await audioResponse.buffer();
+  const audioArrayBuffer = await audioResponse.arrayBuffer();
+  const audioBuffer = Buffer.from(audioArrayBuffer);
 
   // 出力ディレクトリの準備
   const outputDir = path.join(__dirname, "../public/podcast_audio");