Navbar ui

Discription This MR applies a UI-only visual refresh across the dashboard while preserving all existing functionality and API behavior.

What changed Redesigned navbar with: left brand title (StandupTracker) modern profile avatar styling and hover effects improved spacing, shadow, and clean background

Improved top summary cards (Teams/Interns): better typography hierarchy consistent dimensions and spacing rounded corners, soft shadows, and hover lift

Refined Interns/Add Intern sections: cleaner panel surfaces improved search input styling and focus states upgraded empty-state appearance Improved global layout rhythm and responsive spacing. Scope UI/CSS and styling hooks only. No business logic changes. No API integration changes.