fix: integrate PR #3315 review feedback

- ci: add Docker Hub login step, add HF_USER_TOKEN guard on eval step
- docker: tie patches to pinned versions with removal guidance, remove
  unnecessary HF_TOKEN for public dataset, fix hadolint warnings
- docs: fix paper link to arxiv, add teaser image, fix camera names
  (4→3 cameras), fix observation dims (480x640→240x320)

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

.github/workflows/benchmark_tests.yml

@@ -334,6 +334,12 @@ jobs:
         with:
           cache-binary: false
 
+      - name: Login to Docker Hub
+        uses: docker/login-action@v3 # zizmor: ignore[unpinned-uses]
+        with:
+          username: ${{ secrets.DOCKERHUB_LEROBOT_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_LEROBOT_PASSWORD }}
+
       # Build the full-install image: SAPIEN, mplib, CuRobo, pytorch3d +
       # simulation assets (~4 GB). Layer cache lives in the runner's local
       # Docker daemon — reused across re-runs on the same machine.
@@ -349,6 +355,7 @@ jobs:
           cache-to: type=local,dest=/tmp/.buildx-cache-robotwin,mode=max
 
       - name: Run RoboTwin 2.0 smoke eval (1 episode)
+        if: env.HF_USER_TOKEN != ''
         run: |
           # Named container (no --rm) so we can docker cp artifacts out.
           docker run --name robotwin-eval --gpus all \