add gitea actions ci, push docker image to registry

workflow builds on push to main, tags with latest + calver from
package.json, pushes to git.felixfoertsch.de container registry.
docker-compose.yml now pulls from registry instead of building locally.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.dockerignore

@@ -0,0 +1,8 @@
+node_modules/
+dist/
+data/
+.git/
+.gitea/
+.claude/
+.env*
+*.md