[Frontend] Add route-level error boundaries with recovery and correlation IDs

## Problem
A rendering or data failure in one Next.js route can leave users with a blank screen and no actionable support context.

## Scope
Add route/layout error boundaries, safe fallback UI, retry behavior, and a redacted correlation ID shared with API error reporting.

## Acceptance criteria
- Protected and public route groups each have an error boundary.
- Retry resets only the failed segment and does not duplicate mutations.
- Fallbacks work with JavaScript disabled as appropriate and are keyboard accessible.
- Correlation IDs contain no wallet, pet, or health data and appear in support diagnostics.
- Tests cover render exceptions, rejected loaders, retry, navigation, and 404/500 behavior.

Start by locating the Next.js protected and public route/layout groups, the existing API error reporting, and the current test setup. Trace how render and loader failures are handled before covering retry and navigation behavior. Done means the listed render, loader, retry, navigation, 404/500, accessibility, no-JavaScript, and correlation-ID acceptance tests pass.

Written by the indexing model from the issue text.