feat(frontend): add route error boundaries

[Ezeh20]

🚀 Artisyn.io Pull Request

Mark with an x all the checkboxes that apply (like [x])

• Closes Route error boundaries #64
• Added tests (if necessary)
• Run tests
• Run formatting
• Evidence attached
• Commented the code

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📌 Type of Change

• Documentation (updates to README, docs, or comments)
• Bug fix (non-breaking change which fixes an issue)
• Enhancement (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

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📝 Changes description

Added route-level error boundaries for the primary App Router groups:

• src/app/(auth)/error.tsx
• src/app/(dashboard)/error.tsx

These custom error boundaries prevent blank failure screens when runtime errors occur in those route groups. Each boundary shows a user-friendly fallback UI and includes a retry action using Next.js' reset() callback so users can recover without losing overall navigation.

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📸 Evidence (A photo is required as evidence)

Attach screenshots showing:

1. An error rendered inside the auth route with the custom fallback UI
2. An error rendered inside the dashboard route with the retry button visible