fix: preview enum 누락 + AI summary thinking 제거 + CLAUDE.md 전면 갱신

- queue.py: process_stage enum에 'preview' 추가
- classify_worker: ai_summary에 strip_thinking() 적용
- CLAUDE.md: 현재 아키텍처 전면 반영 (파이프라인, UI, 인프라, 코딩규칙)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/workers/classify_worker.py

@@ -62,8 +62,9 @@ async def process(document_id: int, session: AsyncSession) -> None:
             doc.data_origin = parsed["dataOrigin"]
 
         # ─── 요약 ───
+        from ai.client import strip_thinking
         summary = await client.summarize(doc.extracted_text[:15000])
-        doc.ai_summary = summary
+        doc.ai_summary = strip_thinking(summary)
 
         # ─── 메타데이터 ───
         doc.ai_model_version = "qwen3.5-35b-a3b"