Sticky navigation header with mobile menu

[phertyameen]

Issue #6: Sticky navigation header with mobile menu

Category: UI/Homepage
Repo: bridgelet (frontend + docs)

Description

Build a sticky top navbar with logo, nav links (Home, Send, Docs, GitHub), and a hamburger menu for mobile. The menu should close on outside click or Escape key. Active link should be highlighted.

Acceptance Criteria

• Implementation complete
• Tests passing
• Docs updated
• Reviewed and merged