fix(packs-lab): 누락된 A1-A3 파일 복구 (Dockerfile + auth + DSM client + tests)

Tasks A1-A3 의 파일이 working tree에 있었으나 git에 stage되지 않은 상태에서
A4 commit이 진행되어 routes.py 의 import (auth, dsm_client)가 깨진 상태였음.
복구: 8 files 일괄 commit.

- packs-lab/Dockerfile
- packs-lab/app/__init__.py
- packs-lab/app/requirements.txt
- packs-lab/app/auth.py (HMAC verify_request_hmac + verify_upload_token)
- packs-lab/app/dsm_client.py (DSM 7.x Sharing.create wrapper)
- packs-lab/tests/{__init__.py, test_auth.py}
- packs-lab/pytest.ini

packs-lab/tests/__init__.py

@@ -0,0 +1 @@
+# packs-lab tests

packs-lab/tests/test_auth.py

@@ -0,0 +1,85 @@
+"""HMAC 인증 단위 테스트.
+
+- verify_request_hmac: Vercel ↔ backend 요청 시그니처 검증
+- verify_upload_token: 일회성 업로드 토큰 검증 (jti 단발성)
+"""
+import json
+import os
+import time
+import uuid
+
+import pytest
+from fastapi import HTTPException
+
+# 환경변수 먼저 세팅 (auth import 전)
+os.environ["BACKEND_HMAC_SECRET"] = "test-secret-32-bytes-XXXXXXXXXXXX"
+
+from app import auth  # noqa: E402
+
+
+def test_verify_request_hmac_valid():
+    body = b'{"file_path":"/x"}'
+    ts = str(int(time.time()))
+    sig = auth._sign(ts.encode() + b"." + body)
+    auth.verify_request_hmac(body, ts, sig)  # 예외 X
+
+
+def test_verify_request_hmac_expired():
+    body = b'{}'
+    old_ts = str(int(time.time()) - 600)  # 10분 전
+    sig = auth._sign(old_ts.encode() + b"." + body)
+    with pytest.raises(HTTPException) as exc:
+        auth.verify_request_hmac(body, old_ts, sig)
+    assert exc.value.status_code == 401
+
+
+def test_verify_request_hmac_wrong_sig():
+    body = b'{}'
+    ts = str(int(time.time()))
+    with pytest.raises(HTTPException):
+        auth.verify_request_hmac(body, ts, "deadbeef")
+
+
+def test_upload_token_roundtrip():
+    payload = {
+        "tier": "master",
+        "label": "샘플 영상",
+        "filename": "sample.mp4",
+        "size_bytes": 1024,
+        "expires_at": int(time.time()) + 600,
+        "jti": uuid.uuid4().hex,
+    }
+    token = auth.mint_upload_token(payload)
+    decoded = auth.verify_upload_token(token)
+    assert decoded["filename"] == "sample.mp4"
+    assert decoded["jti"] == payload["jti"]
+
+
+def test_upload_token_replay_rejected():
+    payload = {
+        "tier": "starter",
+        "label": "x",
+        "filename": "y.pdf",
+        "size_bytes": 1,
+        "expires_at": int(time.time()) + 600,
+        "jti": uuid.uuid4().hex,
+    }
+    token = auth.mint_upload_token(payload)
+    auth.verify_upload_token(token)  # 첫 사용 OK
+    with pytest.raises(HTTPException) as exc:
+        auth.verify_upload_token(token)  # 재사용
+    assert "이미" in exc.value.detail or "used" in exc.value.detail.lower()
+
+
+def test_upload_token_expired():
+    payload = {
+        "tier": "starter",
+        "label": "x",
+        "filename": "y.pdf",
+        "size_bytes": 1,
+        "expires_at": int(time.time()) - 100,
+        "jti": uuid.uuid4().hex,
+    }
+    token = auth.mint_upload_token(payload)
+    with pytest.raises(HTTPException):
+        auth.verify_upload_token(token)