Fix CI: add build-essential for sharp native compilation

Sharp detects globally-installed libvips and builds from source via
node-gyp, which requires make (provided by build-essential).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: Nik Samokhvalov

.gitlab-ci.yml

@@ -28,7 +28,7 @@ validate_feeds:
   image: oven/bun:1.3-debian
   before_script:
     # Install xmllint for XML validation and libvips for sharp (image processing)
-    - apt-get update && apt-get install -y libxml2-utils jq libvips-dev
+    - apt-get update && apt-get install -y libxml2-utils jq libvips-dev build-essential
     - bun install --frozen-lockfile
   script:
     - bash .ci/validate-feeds.sh