feat(ui): add custom industrial 404 page

[AdityaKumarBharadwaj]

Description

Implemented a custom industrial-themed 404 Not Found page for the web application.

What was added

• Created apps/web/app/not-found.tsx
• Added a responsive custom 404 UI
• Used lucide-react icons for visual feedback
• Added a terminal/syslog styled error panel
• Added an animated warning section and CTA button
• Added navigation back to /dashboard
• Styled the page using existing theme utility classes

Motivation

The default Next.js 404 page did not align with the application's industrial/cyber monitoring aesthetic. This implementation improves the user experience by providing a branded fallback page with clear navigation and consistent visual design.

Closes #9

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Type of Change

• ✨ New feature (non-breaking change which adds functionality)

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How Has This Been Tested?

• Local manual testing

Manual Test Steps

1. Start the development server
2. Navigate to a non-existent route
3. Verify that the custom 404 page renders correctly
4. Verify responsiveness across screen sizes
5. Verify that the "Return to Command Center" button redirects properly

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Screenshot

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AI Generation Declaration

• Yes
• No

Used AI assistance for UI refinement.

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Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• My changes generate no new warnings
• I am a GSSoC participant and I have been officially assigned to the linked issue by a mentor.

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