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/ai-generate-dialog.tsx

@@ -18,6 +18,7 @@ import { Label } from "@/components/ui/label";
 import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from "@/components/ui/select";
 import { cn } from "@/lib/utils";
 import { FakeProgressBar } from "@/components/ui/fake-progress-bar";
+import { useLocale } from "@/lib/i18n/provider";
 
 const LANGUAGES = [
   { code: "en", label: "English" },
@@ -72,11 +73,12 @@ export function AiGenerateDialog({
 }) {
   const t = useTranslations("ai.generate");
   const router = useRouter();
+  const locale = useLocale();
   const [tab, setTab] = useState<Tab>("describe");
 
   // describe tab
   const [prompt, setPrompt] = useState("");
-  const [language, setLanguage] = useState("en");
+  const [language, setLanguage] = useState(locale);
   const [difficulty, setDifficulty] = useState<"" | "easy" | "medium" | "hard">("");
 
   // photo tab