Untrack build output and local artifacts; gitignore them

The image is built in CI (.gitea/workflows/docker-build.yml) from the
Dockerfile and pulled from registry.alwisp.com on Unraid. The Dockerfile
recompiles the client (vite build) inside the build and .dockerignore already
excludes these paths from the build context, so tracking them in git served no
purpose.

- Untrack client/dist (regenerated by the Docker build; logo + version stub
  sources live in client/public).
- Gitignore client/dist/, data/ (local SQLite volume), and *.tar.gz / *.zip
  (local `docker save` exports), alongside the already-ignored node_modules/.

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

.gitignore

@@ -1,4 +1,18 @@
 .claude/
 
-# Dependencies are installed fresh in the Docker build; never vendor them in git.
+# The image is built in CI from the Dockerfile and pulled from the registry on
+# Unraid. Everything below is either regenerated by that build (see .dockerignore)
+# or a local-only artifact, so none of it belongs in git.
+
+# Dependencies — installed fresh during the Docker build
 node_modules/
+
+# Client build output — recompiled inside the Docker build (client: vite build)
+client/dist/
+
+# Local runtime data (production SQLite DB lives on the /data volume)
+data/
+
+# Local image export artifacts (docker save | gzip)
+*.tar.gz
+*.zip