fix: Docker-based production build and CI deployment for documentation

[lucaaamaral]

Summary

• Fix Dockerfile prod, serve, and caddy targets by using additional_contexts to load readmes/ as the docs source, replacing the stale docusaurus/docs/ copy
• Move npm install to the Dockerfile base stage so all targets share dependencies, and add NODE_OPTIONS for memory allocation during multi-locale builds
• Add additional_contexts to all docker-compose.yml services (dev, serve, caddy)
• Fix production CSS theme rendering: remove invalid semicolons after nested CSS rule blocks in custom.css that caused the minifier to produce broken selectors (e.g. ;.navbar), silently skipped by browsers
• Remove non-existent /init.js from docusaurus.config.js scripts
• Escape curly-brace placeholders in 4 doc files so MDX does not interpret them as JSX expressions during production SSG builds
• Rewrite docs-deploy.yml to use Docker build (matching the Dockerfile prod target) instead of bare npm install/npm run build, and move configure-pages to the deploy job

Context

The prod, serve, and caddy Docker targets were broken because they relied on a docusaurus/docs/ directory that was stale and out of sync with the actual documentation in readmes/. The docker-compose.yml dev service worked around this by mounting readmes/ as a volume at runtime, but the production targets had no equivalent mechanism.

The production theme appeared white instead of purple because semicolons after nested CSS rule closing braces (e.g. };) caused the CSS minifier to concatenate them into subsequent selectors, producing invalid CSS like ;.navbar{...} that browsers silently discarded. The dev server processed CSS differently and was unaffected.

The CI workflow used bare npm install/npm run build with Node 22, which diverged from the Dockerfile's Node 24 environment and lacked the additional_contexts mechanism for loading docs.

Test plan

• docker compose build serve completes successfully for all 3 locales (en, es, pt)
• docker compose up serve renders pages with correct purple theme at localhost:3000
• CI workflow build step passes on GitHub Actions (deploy step requires Pages to be enabled on the target repo)
• Verify deployment on magma/magma-documentation with Pages enabled