ci: pin playwright image to a specific digest

Author: serhalp

.github/workflows/ci.yml

@@ -117,7 +117,7 @@ jobs:
     name: 🖥️ Browser tests
     runs-on: ubuntu-24.04-arm
     container:
-      image: mcr.microsoft.com/playwright:v1.58.2-noble
+      image: mcr.microsoft.com/playwright:v1.58.2-noble@sha256:6446946a1d9fd62d9ae501312a2d76a43ee688542b21622056a372959b65d63d
 
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2