Design recent networks section for network switcher

[afeezorobsco-cyber]

##close #506

Summary

This PR enhances the Network Switcher with a Recent Networks section that surfaces the last three networks used, making it faster for users who frequently switch between the same environments.

Changes

Recent Networks

Added a pinned Recent Networks section above the full network list that:

• Displays the last three unique networks used
• Orders networks by most recent usage
• Prevents duplicate entries
• Updates automatically whenever a network is selected

Persistence

Implemented per-user persistence for recent networks so the list is restored across sessions using the project's existing storage mechanism.

Empty State

Added an appropriate empty-state behavior for first-time users with no recent networks.

Popover Design

Documented and implemented:

• Section heading
• Divider between Recent Networks and All Networks
• Active/current network styling
• Hover and focus states
• Responsive layout

Accessibility

Validated against WCAG 2.1 AA:

• Keyboard navigation across sections
• Logical focus order
• Screen reader-friendly headings
• Visible focus indicators
• Contrast compliance

Testing

Executed:

npm run lint

Ran component and visual tests covering:

• New user with no recent networks
• Multiple network selections
• Duplicate selection moves network to the top
• Maximum of three recent entries
• Persistence across sessions
• Keyboard navigation
• Responsive rendering
• Dark mode (where supported)

Review Notes

• Before/after screenshots included.
• Accessibility (axe) validation included.
• Implementation follows existing design patterns and design tokens.

Closes #

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[afeezorobsco-cyber]

@thlpkee20-wq pls review and merge