feat(dashboard): add error boundary with Try Again button (#2250)

[mallya-m]

What does this PR do?

Creates src/app/dashboard/error.tsx as a Next.js App Router error boundary so any dashboard widget crash shows a friendly fallback UI instead of a blank page.

Related issue

Closes #2250

Changes made

• Created src/app/dashboard/error.tsx following Next.js App Router error boundary convention
• Friendly error message styled with var(--card), var(--foreground), var(--accent) to match dashboard theme
• "Try Again" button calls reset() to retry rendering
• Error logged via console.error in useEffect for debugging
• role="alert" and aria-live="assertive" for screen reader accessibility
• Keyboard-focusable button with focus ring and aria-label

How to test

1. Temporarily add throw new Error("test") inside any dashboard widget
2. Navigate to /dashboard
3. Instead of blank page, the error boundary UI appears with "Try Again" button
4. Click "Try Again" — page retries rendering

Screenshots

Checklist

• Linked the related issue above
• Self-reviewed my own diff
• Uses console.error intentionally for debugging
• npm run type-check passes (7 pre-existing upstream errors unrelated to this change)
• Follows Next.js App Router error.tsx conventions exactly
• Styled with CSS variables matching dashboard theme
• Accessible — role="alert", aria-live, keyboard focusable button with aria-label

[github-actions]

GSSoC Label Checklist 🏷️

@Umbrella-io — please apply the appropriate labels before merging:

Difficulty (pick one):

• level:beginner — 20 pts
• level:intermediate — 35 pts
• level:advanced — 55 pts
• level:critical — 80 pts

Quality (optional):

• quality:clean — ×1.2 multiplier
• quality:exceptional — ×1.5 multiplier

Validation (required to score):

• gssoc:approved — counts for points
• gssoc:invalid / gssoc:spam / gssoc:ai-slop — does not score

Type labels (type:*) are auto-detected from files and title. Review and adjust if needed.
Points formula: (difficulty × quality_multiplier) + type_bonus

[mallya-m]

@Priyanshu-byte-coder PR is up!

Created src/app/dashboard/error.tsx using Next.js App Router error boundary conventions. Any widget crash now shows a friendly "Something went wrong" message with a "Try Again" button that calls reset().
Styled with var(--card) and var(--accent) to match the existing dashboard. Error logged to console.error for debugging. Fully accessible with role="alert" and keyboard-focusable button.

Closes #2250
Could you please add:- level:intermediate quality:clean gssoc:approved
Ready to Merge !