[FE-40] Implement command palette (Ctrl+K) for quick navigation

[yusuftomilola]

Overview

Implement a command palette for quick navigation and asset search inside frontend/contrib/.

Location

All work must be inside frontend/contrib/components/ui/.

Acceptance Criteria

• Opens on Ctrl+K (Windows/Linux) / Cmd+K (Mac)
• Modal with a search input at the top
• Default items: quick navigation links (Dashboard, Assets, Reports, Settings, Users)
• When user types, calls GET /assets?search=<query> and shows matching asset results
• Keyboard navigable: arrow keys move selection, Enter navigates
• ESC or click outside closes the palette
• Shortcut registered globally in root layout