BACK-023: Blueprint Search API

**Epic:** Epic 3 - Blueprint Discovery & Filtering

**User Story:** As a backend developer, I need to implement search so users can find blueprints by text

**Acceptance Criteria:**
- Search in title
- Search in tags
- Full-text search implementation
- Search ranking/relevance
- Combine with filters
- Performance optimization

**Size:** M
**Priority:** P2
**Discipline:** Backend