Refactor: [3.0.0] Discord 전송을 n8n으로 이관, YouTube RSS → Data API 전환

- FastAPI에서 Discord 직접 전송 제거, 요약 결과를 JSON으로 반환
- app/discord.py 삭제, DISCORD_WEBHOOK_URL 환경변수 제거
- 에러 시 500 대신 200 + status: error로 응답 (n8n에서 분기 처리)
- CLAUDE.md에 n8n 워크플로우 노드별 상세 설정 문서화

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/main.py

@@ -2,7 +2,6 @@ from fastapi import FastAPI, Header, HTTPException
 from pydantic import BaseModel
 
 from app.config import settings
-from app.discord import send_error_to_discord, send_to_discord
 from app.summarizer import summarize
 from app.transcript import SkipVideo, extract_video_id, fetch_transcript
 
@@ -12,7 +11,6 @@ app = FastAPI(title="News Summary Bot")
 class SummarizeRequest(BaseModel):
     video_url: str
     title: str = ""
-    channel_name: str = ""
 
 
 @app.post("/summarize")
@@ -24,20 +22,22 @@ async def summarize_video(
         raise HTTPException(status_code=401, detail="Unauthorized")
 
     title = req.title or "제목 없음"
-    channel_name = req.channel_name or ""
 
     try:
         video_id = extract_video_id(req.video_url)
         transcript = fetch_transcript(video_id)
         summary = summarize(transcript, title)
-        await send_to_discord(title, req.video_url, summary, channel_name)
     except SkipVideo as e:
         return {"status": "skipped", "title": title, "reason": str(e)}
     except Exception as e:
-        await send_error_to_discord(title, req.video_url, e, channel_name)
-        raise HTTPException(status_code=500, detail=str(e))
+        return {
+            "status": "error",
+            "title": title,
+            "error_type": type(e).__name__,
+            "error_message": str(e),
+        }
 
-    return {"status": "ok", "title": title, "summary_length": len(summary)}
+    return {"status": "ok", "title": title, "summary": summary}
 
 
 @app.get("/health")