Add new blueprints content collection and pages for documenting
architecture decisions, technology strategies and long-term planning.
- Add blueprints collection schema with status tracking (draft/proposal/accepted/implemented/superseded)
- Create index and detail pages for blueprints at /blueprints
- Add first blueprint: Mana Cluster & Federation Architecture
- Add ADR-002 in docs/decisions for internal reference
- Add nav.blueprints translation for all 5 languages
- Add blueprints link to main navigation
