feat(ui): Sprint 10 — Deny Forever on Recipes (card overlay + detail button + undo toast)

User-driven follow-up to Sprint 8: surface the Sprint 1-3 NeverSuggest
infrastructure on the Recipes surface so a family can pre-emptively
mark a recipe as never-suggest before it appears in a plan.

Backend (3 changes):
- POST /api/never-suggest (public, webui-facing). Idempotent on
  (family, recipe, reason). Returns the row joined with recipe_name.
- DELETE /api/never-suggest/{ns_id} (public, webui-facing). Row-level
  ownership check (403 if cross-family), 404 if absent.
- NeverSuggestRead.recipe_name + .ingredient_name server-side joins
  via _attach_names() helper (one LEFT OUTER JOIN per kind).
- Admin path (POST/DELETE /api/admin/never-suggest) unchanged.

Frontend (4 changes):
- New NeverSuggestButton component (~290 lines). Two variants: card
  (overlay on RecipeCard) and detail (text buttons in RecipeDetail
  top bar). Popover with Allergy (red, window.confirm) + Dislike
  (neutral, no confirm). Undo toast via showToast.undo() (Sprint 3
  B12 pattern, 6s window). Pre-existing block detection shows a
  Blocked state with an Unblock path.
- mealPlannerApi.neverSuggest.list/add/remove in api/index.ts.
- Recipes.tsx overlay: RecipeCard has position: relative; button is
  opacity-0 group-hover:opacity-100 focus:opacity-100. e.preventDefault
  + e.stopPropagation prevents accidental navigation.
- RecipeDetail.tsx top bar: new Deny forever button group to the left
  of Add to Plan.

Build: npm run build green (tsc 0 errors, vite 0 errors) on
docker-willester. Bundle 487 -> 495 kB. No new dependencies. No
migration (NeverSuggest table exists from prior sprints).

Tracking: Review/sprint10-verification.md (9-step browser smoke +
5 API curls + undo test + a11y check).

.agent/context.md

@@ -228,3 +228,61 @@ User direction 2026-06-05: "Proceed with the next phase in the redesign." §Futu
 - `frontend/src/pages/ShoppingList.tsx:231` — header anchor
 - `Review/sprint9-verification.md` — new file (deploy + 8-step browser smoke + a11y check)
 
+---
+
+# Context — Sprint 10 ("Deny Forever" on Recipes)
+
+## Why Sprint 10 exists
+
+User direction 2026-06-05: "Proceed with the next phase in the redesign. Also add a phase to include a 'Deny Forever' button in the Recipes endpoint." Sprint 8's "Deny" semantics let the user block a recipe from a meal plan, but the user may want to block a recipe *before* it ever appears in a plan — for example after browsing `/recipes` and finding a recipe the family dislikes.
+
+## Decisions (locked in for Sprint 10)
+
+- **D1. Two-variant button component.** `NeverSuggestButton` has `card` (overlay on `RecipeCard`) and `detail` (text buttons in `RecipeDetail` top bar) variants. Single source of truth for the popover + reason + undo behavior.
+- **D2. Idempotent POST.** The `add` endpoint is idempotent on `(family_profile_id, recipe_id, ingredient_id, reason)`. Re-adding the same row returns the existing one. Avoids accidental duplicates from the popover being double-clicked.
+- **D3. Row-level ownership on DELETE.** The `DELETE` endpoint enforces that the row's `family_profile_id` matches the session's family id; otherwise 403. The `require_session` dep auto-resolves to the first family on the trusted network, so this is "the same family" in practice but coded defensively.
+- **D4. `window.confirm` on `Allergy` only.** `Dislike` skips the confirm (undo toast is the escape hatch). `Allergy` is a more serious action; the confirm dialog prevents accidental permanent blocks.
+- **D5. Undo via toast (Sprint 3 B12 pattern, 6s window).** Reuses `showToast.undo()` from `lib/toast.tsx`. The Undo handler calls `DELETE /api/never-suggest/{id}` and re-invalidates queries so the recipe reappears.
+- **D6. Query invalidations cover the cross-cutting effect.** `['neverSuggest', familyId]` + `['recipes']` + `['recommendedRecipes', familyId]` + `['mealPlan']`. Blocking a recipe affects the Recipes page filter, the Recommended page, and the next planner run.
+- **D7. `recipe_name` join via server-side helper.** `_attach_names()` does one LEFT OUTER JOIN per kind (recipe, ingredient), then merges into response dicts. Avoids the N+1 query pattern; for a family-scale (dozens of rows), one query per kind is sub-millisecond.
+- **D8. Pre-existing block detection.** If a recipe is already blocked, the button shows a "Blocked" state (red `🚫` icon, no `opacity-0`). Clicking it offers an "Unblock" path (with `window.confirm`). This avoids the "I clicked but nothing happened" confusion of the idempotent POST.
+
+## Open questions to surface to the user, not to assume
+
+- **Q1. Should the public DELETE return 403 or 404 on cross-family access?** Default: 403. A 404 would leak less (don't reveal that the row exists), but 403 is the explicit "you don't own this" signal. Trade-off documented in `Review/sprint10-verification.md` R2.
+- **Q2. Should the popover auto-dismiss after a reason is picked?** Default: yes (set `open = false` on success). Otherwise the user could double-click and re-fire the mutation. Documented in the component.
+- **Q3. Should `notes` be required for `Allergy`?** Default: no. The webui doesn't pass `notes` at all (the API client marks it optional). A future "Manage blocked" page could surface it.
+
+## Sprint 10 verification gate
+
+- `cd frontend && npm run build` → green (tsc 0 errors, vite 0 errors)
+- 21/21 planner tests pass (1 pre-existing failure deselected)
+- Browser smoke (9 steps) on `http://100.108.208.56:8082/` per `Review/sprint10-verification.md`
+- 5 API curls (POST, GET, idempotent re-add, DELETE, 403) all return expected status codes
+- No regression in Sprints 1-9
+
+## Sprint 10 — does NOT touch
+
+- The `extractErrorMessage` / `showApiError` flow (Sprint 4 F7) — used for the error toast, unchanged.
+- The keyboard shortcuts (Sprint 5 F2) — unchanged.
+- The bulk pantry add (Sprint 6 F3) — unchanged.
+- The plan-the-week (Sprint 6 F4) — unchanged.
+- The undo-toast (Sprint 3 B12) — reused; unchanged.
+- The WeekRangeNav (Sprint 7) — unchanged.
+- The 3-button Sprint 8 voting row — unchanged.
+- The OnboardingTour (Sprint 9) — unchanged.
+- The admin `POST /api/admin/never-suggest` path — unchanged. Admin token still required.
+- Pre-existing WIP: `backend/app/api/recipes.py`, `backend/app/schemas/recipe.py`, `nginx/nginx.conf` — untouched.
+
+## Key file:line references
+
+- `backend/app/api/never_suggest.py:60-86` — `add_block` (POST)
+- `backend/app/api/never_suggest.py:89-111` — `remove_block` (DELETE)
+- `backend/app/api/never_suggest.py:33-58` — `_attach_names` (recipe_name join)
+- `backend/app/schemas/never_suggest.py:31-33` — `recipe_name` + `ingredient_name` fields
+- `frontend/src/components/NeverSuggestButton.tsx` (NEW, ~290 lines)
+- `frontend/src/api/index.ts:75-86` — `neverSuggest` client
+- `frontend/src/pages/Recipes.tsx:241-300` — `RecipeCard` (overlay button)
+- `frontend/src/pages/RecipeDetail.tsx:73-78` — top bar (Deny forever button group)
+- `Review/sprint10-verification.md` — new file (deploy + 9-step browser smoke + 5 API curls + a11y check)
+