Implement global entity search across all platform entities #79
Description
Problem
Users need a unified search interface to find entities across the entire platform without navigating to specific modules.
Expected Solution
Implement a global search feature that:
- Searches across all entity types (species, missions, equipment, employees, documents, publications, users, expenses, budgets, water quality, air quality, climate data)
- Provides real-time search results
- Offers intuitive UI with entity type grouping
- Supports keyboard navigation
Related
This issue is resolved by PR #75.