feat: Replace browser alert() popups with Toast Notification System

[Ananya-CM]

Summary

Replaced all native browser alert() popups on the
login page with a polished Toast notification system
that matches the app's design language.

Changes Made

New Files Created

1. frontend/app/context/ToastContext.tsx

   • Global ToastProvider with React context
   • showToast(message, type) function
   • Supports: success | error | info types
   • Auto-dismisses after 4 seconds
   • Manual close button (×)

2. frontend/app/components/Toast.tsx

   • Re-exports useToast and ToastProvider
   • Convenience import for components

Modified Files

3. frontend/app/layout.tsx

   • Wrapped app with
   • Available globally across all pages

4. frontend/app/login/page.tsx

   • Replaced 3 alert() calls with showToast()
   • All errors now show as red toast notifications
   • Removed duplicate supabase check

5. frontend/app/globals.css

   • Added slide-in animation keyframes
   • animate-slide-in utility class

Before

• Native browser alert() blocked the entire page
• Unstyled OS-level popup with no branding
• User could not interact until dismissed

After

• ✅ Styled red toast slides in from top-right
• ✅ Page remains fully interactive
• ✅ Auto-dismisses after 4 seconds
• ✅ Manual close button available
• ✅ Matches app's color scheme

Screenshots

Files Changed

• frontend/app/context/ToastContext.tsx ← new
• frontend/app/components/Toast.tsx ← new
• frontend/app/layout.tsx ← wrapped with ToastProvider
• frontend/app/login/page.tsx ← replaced alert()
• frontend/app/globals.css ← added animation

Issue

Closes #83

nsoc26

[vercel]

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[github-actions]

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