feat(ci): add Docker build, push and SSH deploy pipeline

- CI: lint, unit tests, production build on all branches
- Docker build & push on all branches (tag :latest on main, :branch-* on others)
- Deploy: SSH pull & restart on all branches (preprod validation)
- Trigger workflow on self-modification (.github/workflows/ui.yml)

Closes #38

Assisted-by: Claude:claude-sonnet-4-6

ui/.dockerignore

@@ -0,0 +1,8 @@
+node_modules
+dist
+.git
+.github
+*.md
+.dockerignore
+.editorconfig
+.gitignore