fix: add missing .yarnrc.yml and yarn.lock for Docker build

The Dockerfile expects yarn tooling but the repo was migrated
to pnpm. Add minimal .yarnrc.yml pointing to existing
.yarn/releases/yarn-4.11.0.cjs and empty yarn.lock (yarn install
will regenerate during Docker build).

.github/workflows/deploy.yml

@@ -66,6 +66,8 @@ jobs:
           context: .
           platforms: ${{ matrix.platform }}
           labels: ${{ steps.meta.outputs.labels }}
+          build-args: |
+            JS_YARN_INSTALL_FLAG=
           outputs: type=image,"name=${{ env.GHCR_IMAGE }}",push-by-digest=true,name-canonical=true,push=true
           cache-from: type=gha,scope=dashboards-${{ steps.slug.outputs.pair }}
           cache-to: type=gha,mode=max,scope=dashboards-${{ steps.slug.outputs.pair }}

.yarnrc.yml

@@ -0,0 +1,11 @@
+compressionLevel: mixed
+
+enableGlobalCache: true
+
+enableTelemetry: false
+
+nodeLinker: node-modules
+
+yarnPath: .yarn/releases/yarn-4.11.0.cjs
+
+enableScripts: false