feat: copy/export as Markdown wherever print exists

Added a shared ExportMarkdownButton (copy to clipboard / download .md)
next to every existing print button: recipe, shopping list,
collection, meal plan, pantry. Each surface gets a small serializer in
lib/markdown/ built from data already in scope at that page — no new
queries except pantry, where items now thread through as a prop to
PantryPageHeader instead of being fetched only for PantryManager.

Also fixes an unrelated bug hit while verifying the collection export:
RecipeCard called the client-only useTranslations() hook without
"use client", so it rendered fine everywhere it happened to run inside
an already-client tree but 500'd — "Couldn't find next-intl config
file" — when Next tried to run it as a Server Component, which only
happens on the collection detail page (its only caller). Collections
with recipes in them were completely broken.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/lib/markdown/collection.ts

@@ -0,0 +1,32 @@
+type CollectionMarkdownInput = {
+  name: string;
+  description: string | null;
+  recipes: Array<{
+    title: string;
+    description: string | null;
+    baseServings: number;
+    prepMins: number | null;
+    cookMins: number | null;
+    difficulty: "easy" | "medium" | "hard" | null;
+  }>;
+};
+
+export function collectionToMarkdown(collection: CollectionMarkdownInput): string {
+  const lines: string[] = [`# ${collection.name}`, ""];
+
+  if (collection.description) {
+    lines.push(collection.description, "");
+  }
+
+  for (const recipe of collection.recipes) {
+    lines.push(`## ${recipe.title}`, "");
+    if (recipe.description) lines.push(recipe.description, "");
+    const meta: string[] = [`Servings: ${recipe.baseServings}`];
+    if (recipe.prepMins) meta.push(`Prep: ${recipe.prepMins} min`);
+    if (recipe.cookMins) meta.push(`Cook: ${recipe.cookMins} min`);
+    if (recipe.difficulty) meta.push(`Difficulty: ${recipe.difficulty}`);
+    lines.push(meta.join(" · "), "");
+  }
+
+  return lines.join("\n").trim() + "\n";
+}