build(deps): pin SeaweedFS Docker image to 4.18 for stability

Update CI workflow and Dockerfile to use chrislusf/seaweedfs:4.18 instead of
latest. This avoids upload regressions observed with version 4.19 and ensures
consistent builds.

.github/workflows/playwright.yml

@@ -27,8 +27,8 @@ jobs:
         sudo apt-get install -y libreoffice-writer ffmpeg
     - name: Install SeaweedFS weed binary
       run: |
-        WEED_PATH=$(docker run --rm --entrypoint sh chrislusf/seaweedfs:latest -lc 'command -v weed')
-        CID=$(docker create chrislusf/seaweedfs:latest)
+        WEED_PATH=$(docker run --rm --entrypoint sh chrislusf/seaweedfs:4.18 -lc 'command -v weed')
+        CID=$(docker create chrislusf/seaweedfs:4.18)
         docker cp "${CID}:${WEED_PATH}" ./weed
         docker rm "${CID}"
         sudo install -m 0755 ./weed /usr/local/bin/weed

Dockerfile

@@ -13,7 +13,8 @@ RUN git clone --depth 1 https://github.com/ggml-org/whisper.cpp.git && \
     cmake --build build -j
 
 # Stage 1b: extract seaweedfs weed binary (for optional embedded weed mini)
-FROM chrislusf/seaweedfs:latest AS seaweedfs-builder
+# Pin to 4.18 because CI observed upload regressions on 4.19.
+FROM chrislusf/seaweedfs:4.18 AS seaweedfs-builder
 RUN cp "$(command -v weed)" /tmp/weed && \
     (wget -qO /tmp/SeaweedFS-LICENSE.txt "https://raw.githubusercontent.com/seaweedfs/seaweedfs/master/LICENSE" || \
      wget -qO /tmp/SeaweedFS-LICENSE.txt "https://raw.githubusercontent.com/seaweedfs/seaweedfs/main/LICENSE")