Fix build hang: commit lockfile and use npm ci

The pipeline hung on `npm install` because no package-lock.json existed,
forcing a full from-scratch dependency resolve on every build. Commit the
resolved lockfile and switch the Dockerfile to `npm ci` for deterministic,
fast installs. Add .dockerignore to keep the build context small.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.dockerignore

@@ -0,0 +1,17 @@
+# Keep the build context small and reproducible.
+**/node_modules
+**/dist
+**/build
+**/.venv
+**/__pycache__
+**/*.pyc
+**/data
+*.sqlite
+*.db
+.git
+.gitea
+.github
+.env
+.env.*
+*.log
+.DS_Store