fix(i18n): translate remaining recipe card/detail strings, localize AI responses

Recipe cards, the recipe detail page, and meal planner still rendered raw
"{n} servings"/"{n}m cook"/"{n} srv" text and untranslated difficulty labels
outside the earlier i18n pass. Also wires the user's locale into AI features
that previously always answered in English regardless of app language:
recipe chat, ingredient substitution, recipe ideas, and generate-from-idea.
The recipe-language picker in the AI generate dialog now defaults to the
user's locale instead of always defaulting to English.

apps/web/components/recipe/generate-content-button.tsx

@@ -7,6 +7,7 @@ import { Sparkles, Loader2 } from "lucide-react";
 import { toast } from "sonner";
 import { Button } from "@/components/ui/button";
 import { FakeProgressBar } from "@/components/ui/fake-progress-bar";
+import { useLocale } from "@/lib/i18n/provider";
 
 type GeneratedRecipe = {
   ingredients: Array<{ rawName: string; quantity?: number; unit?: string; note?: string }>;
@@ -24,6 +25,7 @@ export function GenerateContentButton({
 }) {
   const t = useTranslations("ai.generate");
   const router = useRouter();
+  const locale = useLocale();
   const [busy, setBusy] = useState(false);
 
   async function generate() {
@@ -36,7 +38,7 @@ export function GenerateContentButton({
       const genRes = await fetch("/api/v1/ai/generate", {
         method: "POST",
         headers: { "Content-Type": "application/json" },
-        body: JSON.stringify({ prompt }),
+        body: JSON.stringify({ prompt, language: locale }),
       });
 
       if (!genRes.ok) {