feat: locale-based generation, describe field for batch cooking; fix bulk-bar width and sourceUrl not saving

- AI recipe generation always used the app's own locale rather than a
  separate language picker — removed the picker, generation and the
  saved recipe's language now both follow useLocale() directly.
- Bulk-select action bar had an ungated max-w-md that capped it at 448px
  even past the sm: breakpoint where sm:w-auto was supposed to let it
  grow to content — added sm:max-w-none so desktop never scrolls.
- Batch-cooking generation had no free-text "describe" field like the
  standard recipe generator does — added one (BatchCookFields, both the
  standalone dialog and the AI dialog's batch tab), threaded through the
  API route and generateBatchCook's prompt as additional guidance.
- Recipes imported from a URL never actually got their sourceUrl
  persisted — CreateRecipeSchema didn't declare the field, so Zod
  silently stripped it before it ever reached the insert. The detail
  page's "Source: <hostname>" link already existed but was dead code
  for every real import until now.

Verified all 4 live: generate dialog has no language selector, batch
tab has a working describe textarea, bulk-select bar renders at full
content width with zero horizontal overflow on desktop, and a recipe
created with sourceUrl now round-trips and renders its source link.

apps/web/messages/fr.json

@@ -546,6 +546,8 @@
     "dishCount": "{count, plural, one {# plat} other {# plats}}",
     "wizardTitle": "Planifier une session de batch cooking",
     "wizardDescription": "Choisissez combien de repas couvrir — on génère une liste de courses partagée et une seule session de préparation pour tout.",
+    "describe": "Décrivez ce que vous recherchez",
+    "describePlaceholder": "ex. saveurs méditerranéennes, utiliser la courge du garde-manger, adapté aux enfants…",
     "dinners": "Dîners",
     "lunches": "Déjeuners",
     "servingsPerMeal": "Portions par repas",