security: fix 5 review findings (2 high, 3 medium)

HIGH:
- Lock setup TOTP/NAS endpoints behind _require_setup() guard
  (prevented unauthenticated admin 2FA takeover after setup)
- Sanitize upload filename with Path().name + resolve() validation
  (prevented path traversal writing outside Inbox)

MEDIUM:
- Add score > 0.01 filter to hybrid search via subquery
  (prevented returning irrelevant documents with zero score)
- Implement Inbox → Knowledge file move after classification
  (classify_worker now moves files based on ai_domain)
- Add Anthropic Messages API support in _request()
  (premium/Claude path now sends correct format and parses
  content[0].text instead of choices[0].message.content)

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

app/api/documents.py

@@ -127,16 +127,25 @@ async def upload_document(
     if not file.filename:
         raise HTTPException(status_code=400, detail="파일명이 필요합니다")
 
+    # 파일명 정규화 (경로 이탈 방지)
+    safe_name = Path(file.filename).name
+    if not safe_name or safe_name.startswith("."):
+        raise HTTPException(status_code=400, detail="유효하지 않은 파일명")
+
     # Inbox에 파일 저장
     inbox_dir = Path(settings.nas_mount_path) / "PKM" / "Inbox"
     inbox_dir.mkdir(parents=True, exist_ok=True)
-    target = inbox_dir / file.filename
+    target = (inbox_dir / safe_name).resolve()
+
+    # Inbox 하위 경로 검증
+    if not str(target).startswith(str(inbox_dir.resolve())):
+        raise HTTPException(status_code=400, detail="잘못된 파일 경로")
 
     # 중복 파일명 처리
     counter = 1
     stem, suffix = target.stem, target.suffix
     while target.exists():
-        target = inbox_dir / f"{stem}_{counter}{suffix}"
+        target = inbox_dir.resolve() / f"{stem}_{counter}{suffix}"
         counter += 1
 
     content = await file.read()