feat(content): add GLPI 12.0.0 official release blog post

[eduardofraga]

Summary

• Author comprehensive blog posts announcing the official release of GLPI 12.0.0 and EF-TECH cloud-native distribution (v12.0.0, PR #214, Helm chart glpi-2.12.0) in Portuguese (content/pt-br/blog/glpi-12-0-0/index.md) and English (content/en/blog/glpi-12-0-0/index.md).
• Highlight upstream GLPI 12.0.0 features: rewritten Knowledge Base frontend, active Session Management, Step-Up Authentication (Sudo Mode), group-managed OLAs, RGAA/RAWeb accessibility compliance, security hardening, new user documentation, and the End-of-Life (EOL) of GLPI 10.x (final release 10.0.28).
• Highlight EF-TECH cloud-native distribution features: unprivileged Alpine containers (UID/GID 10001), Valkey (helmforge/valkey) and MariaDB (helmforge/mariadb) subcharts, custom Nginx templates (PR #209), MySQL/MariaDB SSL support (PR #207), PDB/HPA high availability, container hardening (readOnlyRootFilesystem), maintenance CronJob, and S3 file backup.
• Provide step-by-step deployment instructions for Helm (helm upgrade --install glpi eftech/glpi --version 2.12.0), complete values.yaml production configuration, and docker-compose.yml.
• Include migration guide from GLPI 10.x / 11.x to 12.0.0.
• Generate and publish high-resolution 1200x630 cover PNG images with vector checkmarks and terminal preview across bundles and static assets.
• Cross-link in .context/docs/README.md, .context/agents/README.md, and .context/plans/README.md.
• Validated via hugo --gc --minify and lychee link checker with 0 errors.