feat(web): restore actionable user feedback

[Alex0158]

Summary

• mount the Consumer Web Sonner renderer once at the app root
• add persistent, accessible form feedback for Consumer auth and Admin login failures
• prevent duplicate Auth error toasts and stop reporting clipboard failure as success
• record the seven audited feedback gaps and the shared content/feedback governance rule

Verification

• Consumer tests: 185 files / 2046 tests passed
• Admin tests: 16 files / 53 tests passed
• Consumer + Admin lint and production builds passed
• docs:check, Web A11Y contracts, product-line, Admin boundary, critical E2E skip guard, and git diff check passed
• local browser reproduced the Production defect and verified one transport toast plus one persistent form alert after the fix