feat(errors): forward CAMS warnings and swallowed exceptions as breadcrumbs

## Problem
(verified) Failures currently vanish into `warning(...)` console logs that are no-ops in release — e.g., token-refresh failure (`lib/data/carp_backend.dart:72-75`), auth failure (:97-99), consent-upload failure (:232-236). There is no file or remote sink.

## Proposed fix
Route the app's `warning()`/`error()` paths into the crash reporter as breadcrumbs/non-fatals (post-scrubbing, see the privacy EPIC), so field issues like #443 and #498 become diagnosable.

## Acceptance criteria
- [ ] A failed token refresh in the field is visible as a non-fatal with a breadcrumb trail

**Effort:** S · **Priority:** P2 · **Change risk:** Low