feat: collections visibility enum (matches recipes) + QR on collection PDF (v0.54.0)

Replaces collections.isPublic (boolean) with collections.visibility
(private/unlisted/public/followers — same enum recipes use). Two-step
migration (0050 adds+backfills, 0051 drops isPublic) since drizzle-kit's
add+drop-in-one-diff rename heuristic needs an interactive prompt we
can't satisfy here.

New collectionVisibleToViewer(viewerId) in lib/visibility.ts mirrors the
existing recipe helper (author always sees own; public/unlisted visible
to anyone; followers-only via the same user_follows EXISTS pattern) —
used by the collection detail page, its print view, fork, and favorite,
replacing their old `or(isPublic, own)` checks.

Create/edit collection dialogs get the same 4-option visibility select
as the recipe form instead of a public/private checkbox.

Collection PDF export now generates a QR code (qrcode, same as the
recipe PDF) linking to /collections/{id}, shown only when visibility is
public/unlisted — same "would an anonymous scanner actually resolve
this" rule as the recipe QR.

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

apps/web/app/print/collection/[id]/page.tsx

@@ -1,7 +1,9 @@
 import { notFound } from "next/navigation";
 import { headers } from "next/headers";
+import QRCode from "qrcode";
 import { auth } from "@/lib/auth/server";
-import { db, collections, eq, and, or } from "@epicure/db";
+import { db, collections, eq, and } from "@epicure/db";
+import { collectionVisibleToViewer } from "@/lib/visibility";
 import { PrintTrigger } from "@/components/recipe/print-trigger";
 import { formatIngredientQuantity } from "@/lib/unit-conversion";
 import { getMessages, formatMessage } from "@/lib/i18n/server";
@@ -17,10 +19,7 @@ export default async function CollectionPrintPage({ params }: Params) {
   const unitPref = (session.user as { unitPref?: string }).unitPref === "imperial" ? "imperial" : "metric";
 
   const col = await db.query.collections.findFirst({
-    where: and(
-      eq(collections.id, id),
-      or(eq(collections.userId, session.user.id), eq(collections.isPublic, true))
-    ),
+    where: and(eq(collections.id, id), collectionVisibleToViewer(session.user.id)),
     with: {
       recipes: {
         with: {
@@ -39,6 +38,13 @@ export default async function CollectionPrintPage({ params }: Params) {
 
   const recipeEntries = col.recipes.filter((r) => r.recipe !== null);
 
+  // Same rationale as the recipe print page's QR: only link a URL an
+  // anonymous scanner could actually resolve.
+  const shareUrl = col.visibility === "public" || col.visibility === "unlisted"
+    ? `${process.env["BETTER_AUTH_URL"] ?? "http://localhost:3000"}/collections/${id}`
+    : null;
+  const qrDataUrl = shareUrl ? await QRCode.toDataURL(shareUrl, { margin: 1, width: 120 }) : null;
+
   return (
     <>
       <style>{`
@@ -71,6 +77,9 @@ export default async function CollectionPrintPage({ params }: Params) {
         .timer { font-size: 0.85em; color: #666; font-family: system-ui, sans-serif; margin-left: 8px; }
         .cookbook-cover { text-align: center; margin-bottom: 40px; }
         .cookbook-cover h1 { font-size: 2.6em; }
+        .qr-block { text-align: center; margin: 0 auto; font-family: system-ui, sans-serif; }
+        .qr-block img { width: 84px; height: 84px; display: block; margin: 0 auto; }
+        .qr-block span { display: block; font-size: 0.65em; color: #999; margin-top: 4px; }
         footer { margin-top: 40px; font-size: 0.75em; color: #aaa; text-align: center; font-family: system-ui, sans-serif; }
         .print-btn {
           position: fixed; top: 16px; right: 16px; padding: 8px 16px;
@@ -88,6 +97,13 @@ export default async function CollectionPrintPage({ params }: Params) {
         <p style={{ fontFamily: "system-ui, sans-serif", fontSize: "0.85em", color: "#888" }}>
           {recipeEntries.length} recipe{recipeEntries.length !== 1 ? "s" : ""}
         </p>
+        {qrDataUrl && (
+          <div className="qr-block">
+            {/* eslint-disable-next-line @next/next/no-img-element -- data: URI, next/image can't optimize it anyway */}
+            <img src={qrDataUrl} alt={m.collections.qrCodeAlt} />
+            <span>{m.collections.qrCodeCaption}</span>
+          </div>
+        )}
       </div>
 
       {recipeEntries.map(({ recipe }) => {