feat: anonymous read-only public link + QR code for meal plans (v0.68.0)

Mirrors shopping lists' isPublic pattern but read-only only -- no
publicEditable equivalent, since anonymous editing of someone's
weekly meal schedule isn't a real use case the way collaborative
shopping-list editing is. New PATCH /api/v1/meal-plans/{weekStart}
toggles it (lazily creates the week's plan row if missing, same
pattern as the existing POST). Public page at /m/[id] renders the
week grouped by day, linking through to public/unlisted recipes and
just showing the title otherwise.

ShareMealPlanButton gained the same public-link toggle UI as its
shopping-list sibling, plus a QR code (generated client-side via the
already-installed `qrcode` package) for the link once enabled --
handing someone a printed or screenshotted plan doesn't require
typing a URL.

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

apps/web/components/meal-plan/share-meal-plan-button.tsx

@@ -1,9 +1,10 @@
 "use client";
 
-import { useState } from "react";
+import { useEffect, useState } from "react";
 import { useTranslations } from "next-intl";
-import { UserPlus, X } from "lucide-react";
+import { UserPlus, X, Link2, Copy, Check } from "lucide-react";
 import { toast } from "sonner";
+import QRCode from "qrcode";
 import {
   Dialog,
   DialogContent,
@@ -13,6 +14,7 @@ import {
 } from "@/components/ui/dialog";
 import { Button } from "@/components/ui/button";
 import { Input } from "@/components/ui/input";
+import { Switch } from "@/components/ui/switch";
 import {
   Select,
   SelectContent,
@@ -21,6 +23,7 @@ import {
   SelectValue,
 } from "@/components/ui/select";
 import { Badge } from "@/components/ui/badge";
+import { Separator } from "@/components/ui/separator";
 import { Tooltip, TooltipContent, TooltipProvider, TooltipTrigger } from "@/components/ui/tooltip";
 
 type Role = "viewer" | "editor";
@@ -39,9 +42,11 @@ interface Member {
 
 interface Props {
   weekStart: string;
+  mealPlanId?: string;
+  initialIsPublic?: boolean;
 }
 
-export function ShareMealPlanButton({ weekStart }: Props) {
+export function ShareMealPlanButton({ weekStart, mealPlanId, initialIsPublic = false }: Props) {
   const t = useTranslations("mealPlan");
   const ts = useTranslations("shareDialog");
   const tCommon = useTranslations("common");
@@ -51,6 +56,61 @@ export function ShareMealPlanButton({ weekStart }: Props) {
   const [members, setMembers] = useState<Member[]>([]);
   const [loading, setLoading] = useState(false);
   const [inviting, setInviting] = useState(false);
+  const [isPublic, setIsPublic] = useState(initialIsPublic);
+  const [planId, setPlanId] = useState(mealPlanId);
+  const [savingPublic, setSavingPublic] = useState(false);
+  const [copied, setCopied] = useState(false);
+  const [qrDataUrl, setQrDataUrl] = useState<string | null>(null);
+
+  function shareUrl(id: string): string {
+    return `${window.location.origin}/m/${id}`;
+  }
+
+  useEffect(() => {
+    if (initialIsPublic && mealPlanId) {
+      QRCode.toDataURL(shareUrl(mealPlanId), { margin: 1, width: 160 }).then(setQrDataUrl).catch(() => {});
+    }
+    // Only needs to run once per mount with the plan's already-saved state —
+    // subsequent changes are handled by togglePublic itself.
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, []);
+
+  async function togglePublic(checked: boolean) {
+    setSavingPublic(true);
+    const previous = isPublic;
+    setIsPublic(checked);
+    try {
+      const res = await fetch(`/api/v1/meal-plans/${weekStart}`, {
+        method: "PATCH",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ isPublic: checked }),
+      });
+      if (!res.ok) throw new Error();
+      const data = (await res.json()) as { id: string; isPublic: boolean };
+      setPlanId(data.id);
+      if (checked) {
+        setQrDataUrl(await QRCode.toDataURL(shareUrl(data.id), { margin: 1, width: 160 }));
+      } else {
+        setQrDataUrl(null);
+      }
+    } catch {
+      setIsPublic(previous);
+      toast.error(ts("publicLinkToggleFailed"));
+    } finally {
+      setSavingPublic(false);
+    }
+  }
+
+  async function copyLink() {
+    if (!planId) return;
+    try {
+      await navigator.clipboard.writeText(shareUrl(planId));
+      setCopied(true);
+      setTimeout(() => setCopied(false), 2000);
+    } catch {
+      toast.error(ts("copyLinkFailed"));
+    }
+  }
 
   async function fetchMembers() {
     setLoading(true);
@@ -137,6 +197,31 @@ export function ShareMealPlanButton({ weekStart }: Props) {
             </DialogDescription>
           </DialogHeader>
 
+          <div className="flex items-center justify-between gap-3 rounded-lg border p-3">
+            <div className="flex items-center gap-2 min-w-0">
+              <Link2 className="h-4 w-4 text-muted-foreground shrink-0" />
+              <div className="min-w-0">
+                <p className="text-sm font-medium">{ts("publicLinkTitle")}</p>
+                <p className="text-xs text-muted-foreground">{t("publicLinkReadOnlyDescription")}</p>
+              </div>
+            </div>
+            <Switch checked={isPublic} disabled={savingPublic} onCheckedChange={(v) => { void togglePublic(v); }} />
+          </div>
+          {isPublic && planId && (
+            <div className="flex items-center gap-3 rounded-lg border p-3">
+              {qrDataUrl && (
+                // eslint-disable-next-line @next/next/no-img-element -- a data: URL generated client-side, not an optimizable remote image
+                <img src={qrDataUrl} alt={t("qrCodeAlt")} className="h-16 w-16 shrink-0" />
+              )}
+              <Button type="button" variant="outline" size="sm" className="flex-1" onClick={() => void copyLink()}>
+                {copied ? <Check className="h-4 w-4" /> : <Copy className="h-4 w-4" />}
+                {copied ? ts("linkCopied") : ts("copyLink")}
+              </Button>
+            </div>
+          )}
+
+          <Separator />
+
           <div className="flex gap-2 mt-2">
             <Input
               type="email"