feat: dark mode, skeleton loaders, batch upsert optimization, and error boundaries (#122, #124, #125, #128)

[Sweet-Kid]

Summary

This PR resolves 4 open issues to improve the merchant dashboard experience:

closes #128 – Dark Mode Support

• Updated ThemeToggle to support 3-way cycling: light → dark → system
• Added Monitor icon from lucide-react for system theme indicator
• Theme persists to localStorage via next-themes

closes #125 – Skeleton Loaders

• Created reusable WidgetSkeleton component with 4 variants: card, chart, table, stat
• Integrated WidgetSkeleton into dashboard loading states
• Prevents layout shift (CLS) during data fetch

closes #124 – Optimize Postgres Upsert Queries

• Refactored sync route to use batch insert via insertPaymentsInTransaction
• Fixed broken function structure in respond() and POST() handlers
• Removed duplicate imports and undefined variable references
• Single transaction for all batch operations improves performance

closes #122 – API Error Boundaries

• Created dashboard layout wrapping all routes with ErrorBoundary
• Wrapped individual dashboard sections (settlement summary, settlements table) for widget isolation
• Custom fallback UI with retry button and clear error messaging
• Crashes in one widget don't take down the entire dashboard

Files Changed

• apps/web/src/components/theme-toggle.tsx – 3-way theme toggle
• apps/web/src/components/widget-skeleton.tsx – New skeleton component
• apps/web/src/app/dashboard/page.tsx – Integrate skeletons and error boundaries
• apps/web/src/app/dashboard/layout.tsx – New dashboard layout with ErrorBoundary
• apps/web/src/app/api/sync/route.ts – Batch upsert optimization and bug fixes

[drips-wave]

@Sweet-Kid Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits

[vercel]

@Sweet-Kid is attempting to deploy a commit to the ACCENSA Team on Vercel.

A member of the Team first needs to authorize it.

[mergekeeper]

MergeKeeper review

Scope: in scope for linked issue #128.
Verdict: clean

The pull request correctly implements dark mode cycling, skeleton loaders, database upsert query optimizations, and API error boundaries as specified by the linked issues.

Reviewed commit: fe70050fcd444a8da017749172641a26010a63fd.
CI and merge eligibility are checked separately.

[mergekeeper]

MergeKeeper merge status

Status: blocked
PR state: open
Mergeability: mergeable
Checked commit: fe70050fcd444a8da017749172641a26010a63fd.

Reason: One or more required CI checks failed.

Failing checks:

• format - view details
• e2e (web) - view details
• test (sdk) - view details
• build - view details
• test (reconcile-payments) - view details
• typecheck - view details
• lint - view details
• test (web) - view details
• playwright (web) - view details

Next steps:

1. Open the failing check details above and fix the reported error.
2. Run the same checks locally where possible.
3. Commit and push the fix.
4. MergeKeeper will automatically re-review the updated PR.