feat: Markdown 편집기 + PDF 변환 파이프라인 + 뷰어 포맷 분기

- Markdown split editor: textarea + marked preview, Ctrl+S 저장
- PUT /api/documents/{id}/content: 원본 파일 저장 + extracted_text 갱신
- GET /api/documents/{id}/preview: PDF 미리보기 캐시 서빙
- preview_worker: LibreOffice headless → PDF 변환 (timeout 60s, retry 1회)
- queue_consumer: preview stage 추가 (embed 후 자동 트리거)
- DocumentViewer: 포맷별 분기 (markdown/pdf/preview-pdf/image/text/cad)
- 오피스/CAD 문서: 새 탭 편집 버튼
- Dockerfile: LibreOffice headless 설치
- migration 005: preview_status, preview_hash, preview_at 컬럼

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

app/api/documents.py

@@ -37,6 +37,7 @@ class DocumentResponse(BaseModel):
     ai_tags: list | None
     ai_summary: str | None
     user_note: str | None
+    preview_status: str | None
     source_channel: str | None
     data_origin: str | None
     extracted_at: datetime | None
@@ -298,6 +299,66 @@ async def update_document(
     return DocumentResponse.model_validate(doc)
 
 
+@router.put("/{doc_id}/content")
+async def save_document_content(
+    doc_id: int,
+    user: Annotated[User, Depends(get_current_user)],
+    session: Annotated[AsyncSession, Depends(get_session)],
+    body: dict = None,
+):
+    """Markdown 원본 파일 저장 + extracted_text 갱신"""
+    doc = await session.get(Document, doc_id)
+    if not doc:
+        raise HTTPException(status_code=404, detail="문서를 찾을 수 없습니다")
+
+    if doc.file_format not in ("md", "txt"):
+        raise HTTPException(status_code=400, detail="편집 가능한 포맷이 아닙니다 (md, txt만 가능)")
+
+    content = body.get("content", "") if body else ""
+    file_path = Path(settings.nas_mount_path) / doc.file_path
+    file_path.write_text(content, encoding="utf-8")
+
+    # 메타 갱신
+    doc.file_size = len(content.encode("utf-8"))
+    doc.file_hash = file_hash(file_path)
+    doc.extracted_text = content[:15000]
+    doc.updated_at = datetime.now(timezone.utc)
+    await session.commit()
+
+    return DocumentResponse.model_validate(doc)
+
+
+@router.get("/{doc_id}/preview")
+async def get_document_preview(
+    doc_id: int,
+    session: Annotated[AsyncSession, Depends(get_session)],
+    token: str | None = Query(None, description="Bearer token (iframe용)"),
+):
+    """PDF 미리보기 캐시 서빙"""
+    from core.auth import decode_token
+
+    if token:
+        payload = decode_token(token)
+        if not payload or payload.get("type") != "access":
+            raise HTTPException(status_code=401, detail="유효하지 않은 토큰")
+    else:
+        raise HTTPException(status_code=401, detail="토큰이 필요합니다")
+
+    doc = await session.get(Document, doc_id)
+    if not doc:
+        raise HTTPException(status_code=404, detail="문서를 찾을 수 없습니다")
+
+    preview_path = Path(settings.nas_mount_path) / "PKM" / ".preview" / f"{doc_id}.pdf"
+    if not preview_path.exists():
+        raise HTTPException(status_code=404, detail="미리보기가 아직 생성되지 않았습니다")
+
+    return FileResponse(
+        path=str(preview_path),
+        media_type="application/pdf",
+        headers={"Content-Disposition": "inline"},
+    )
+
+
 @router.delete("/{doc_id}")
 async def delete_document(
     doc_id: int,