ci: fix private registry access in Docker build stage

Dockerfile

@@ -24,11 +24,14 @@ RUN corepack enable && corepack prepare pnpm@10.3.0 --activate
 # Copy lockfile and manifest for dependency installation caching
 COPY pnpm-lock.yaml package.json .npmrc* ./
 
-# Install dependencies with cache mount
+# Configure private registry and install dependencies
 RUN --mount=type=cache,id=pnpm,target=/pnpm/store \
     --mount=type=secret,id=NPM_TOKEN \
     export NPM_TOKEN=$(cat /run/secrets/NPM_TOKEN 2>/dev/null || echo $NPM_TOKEN) && \
-    pnpm install --frozen-lockfile
+    echo "@mintel:registry=https://npm.infra.mintel.me" > .npmrc && \
+    echo "//npm.infra.mintel.me/:_authToken=\${NPM_TOKEN}" >> .npmrc && \
+    pnpm install --frozen-lockfile && \
+    rm .npmrc
 
 # Copy source code
 COPY . .