Proxy routes now share one upstream-error adapter so client-actionable statuses such as auth, entitlement, validation, and rate limits survive the BFF instead of becoming opaque 502s. The scan terminal mobile overrides also load last and remove desktop rail constraints so phones get a single readable column.
Constraint: Mobile users reported the dashboard was unreadable, and BFF proxy errors were masking expected client states.
Rejected: Let every route keep bespoke error JSON | continued inconsistent status codes and production detail leakage.
Confidence: high
Scope-risk: moderate
Directive: Keep ScanTerminalMobile.module.css imported after desktop scan-terminal CSS so mobile breakpoints win.
Tested: npx tsc --noEmit --pretty false --project frontend/tsconfig.json
Tested: npm run build
Tested: npm run test:business
Tested: Chrome mobile smoke test at 390px with no horizontal overflow
Not-tested: Real device Safari/Android manual QA