feat(dashboard): [dashboard] create user avatar dropdown menu in navbar closes #604

[amankoli09]

Closes #604

Description

This PR addresses issue #604 by implementing a new UserAvatarDropdown component within the dashboard navbar. It replaces the old static "Connect Wallet" / placeholder avatar section with a fully interactive dropdown menu that enhances the user experience.

Changes Included

• UserAvatarDropdown Component: Created a new, animated dropdown menu that displays user initials with a deterministic gradient background.
• Copy to Clipboard Functionality: Users can now click to copy their email address directly from the dropdown header, with visual feedback.
• Menu Actions: Integrated navigation links directly into the dropdown (Settings, Notifications) seamlessly tied into the existing App.tsx tab state.
• Accessibility & UX Improvements: Added Framer Motion animations for smooth entrance/exit, keyboard accessibility (Escape to close), focus states, and click-outside handling.
• Navbar Integration: Replaced the static header area in App.tsx with the new component.

Validation

• Changes validated locally.
• Verified that npm run build succeeds without issues.
• No local SQLite files or lock files were included in the commit.
• Code conforms to formatting guidelines.

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