feat(ui): close 3 P2 audit findings + a11y sweep (Sprint 3)

- lib/toast.tsx (renamed from .ts for JSX): new showToast.undo(message,
  onUndo, ms=5000) helper. Inline 'Undo' button dismisses the toast and
  fires onUndo. Note: react-hot-toast 2.6 lacks onClose/onDismiss, so
  expiry is silent — same effective behavior as confirm() declined.

- Dashboard.handleDelete: captures the full MealPlanItem before the
  DELETE so Undo can re-fire meals.generateItem(planId, dayOfWeek,
  mealType) and refill the slot (recipe may differ — see plan R4).

- Pantry.handleRemove: fully reversible — Undo re-fires pantry.add with
  the original ingredient_id, quantity, and unit. New removeId state
  scopes the spinner to the clicked row.

- Both confirm() call sites removed.

- App.tsx Navigation: whitespace-nowrap + px-2 sm:px-3 so all 4 links fit
  on one line down to 360 px. aria-current='page' on the active link.
  <nav aria-label='Primary'>, <main id='main-content'>.

- components/ui/Badge: optional icon and aria-label props. Dashboard
  approval-status Badge passes aria-label='Approval status: approved'
  (or the current value) so screen readers don't rely on color alone.

- ErrorBoundary already mounted at App.tsx:42 — verified, no code change.

- Review/sprint3-verification.md (new) + Review/ui-nielsen-audit.md and
  fix-ui-audit.md updated with Sprint 3 status and deploy steps.

Build: npm run build (tsc + vite) green. tsc 0 errors.

Review/sprint3-verification.md

@@ -0,0 +1,40 @@
+# Sprint 3 — Verification Log
+
+**Date:** 2026-06-03
+**Scope:** Three P2s (B12, B13, B14) + a11y sweep (S3.5) + ErrorBoundary confirmation (S3.4 — no code change).
+**Build:** `cd frontend && npm run build` → green (0 tsc errors, 0 eslint warnings, dist emitted).
+
+## Files changed
+
+| File | Change |
+|---|---|
+| `frontend/src/lib/toast.ts` → `toast.tsx` | New `showToast.undo(message, onUndo, ms=5000)` helper. Renamed to `.tsx` for JSX support. |
+| `frontend/src/pages/Dashboard.tsx` | B12: `handleDelete` captures full `MealPlanItem`; on undo calls `meals.generateItem(planId, dayOfWeek, mealType)`. Status Badge gets explicit `aria-label`. |
+| `frontend/src/pages/Pantry.tsx` | B12: `handleRemove` is fully reversible; calls `pantry.add` with original `ingredient_id`/`quantity`/`unit` on undo. New `removeId` state for per-row loading. |
+| `frontend/src/App.tsx` | B13: nav `whitespace-nowrap` + `px-2 sm:px-3`. S3.5: `aria-current="page"` on active link; `<nav aria-label="Primary">`; `<main id="main-content">`. |
+| `frontend/src/components/ui/Badge.tsx` | S3.5: optional `icon` and `aria-label` props. |
+| `Review/ui-nielsen-audit.md`, `fix-ui-audit.md` | Updated with Sprint 3 status. |
+
+## How to deploy
+
+```bash
+cd ~/MealPlanner
+git pull
+docker compose -f docker-compose.yml up -d --build frontend
+```
+
+No backend changes in Sprint 3. No migration.
+
+## Manual smoke checks
+
+- **Dashboard** (mobile 360 px): all 4 nav links fit on one line. Tab to Meal Planner link → `aria-current="page"` is announced.
+- **Dashboard** (delete flow): click a meal's `X` button → toast appears "Meal deleted" with **Undo**. Click Undo within 5s → a new meal fills the slot. Let the toast expire → slot stays empty.
+- **Pantry** (delete flow): click Remove on a row → toast appears "Item removed" with **Undo**. Click Undo within 5s → the original item is back with its original quantity/unit. Per-row spinner visible only on the clicked row.
+- **A11y** (DevTools): `<main id="main-content">` is the skip-link target. `<nav aria-label="Primary">`. Active nav link has `aria-current="page"`. Approval-status Badge in meal card has `aria-label="Approval status: approved"` etc.
+- **Meal card (mobile 360 px)**: confirm the title is still 2-line clamped (Sprint 2 fix intact) and the approve-status pill is color + text + aria-label (no color-only signal).
+
+## Notes / Caveats
+
+- `react-hot-toast` 2.6's `ToastOptions` does not expose `onClose` or `onDismiss`. The `undo` helper relies solely on the user clicking the Undo button during the 5s window — there is no "expire callback". This is documented in `lib/toast.tsx`. The previous `confirm()` had the same effective behavior (the user could click Cancel within the dialog).
+- For Dashboard delete, the Undo fills the slot with a freshly generated recipe (likely different from the deleted one). The original recipe cannot be restored without backend support for a "rebuild from snapshot" endpoint. This trade-off is documented in the plan's §R4.
+- Per-row loading state in Pantry: the `Remove` button shows a spinner only on the row being deleted, not all rows simultaneously.