feat: public collections viewable anonymously at /c/{id} (v0.54.1)

New /c/[id] route mirrors /r/[id]'s pattern for recipes: no session
required, gated on collections.visibility != 'private', with an explicit
followers-only check (viewer must be signed in and follow the owner)
since this route has no other access control. Added to proxy.ts's
PUBLIC_PATHS.

Only shows recipes inside the collection that the anonymous/signed-in
viewer could actually see on their own (public/unlisted always, followers
recipes only if following that recipe's author) — the owner's own private
recipes stay hidden from everyone else even inside their own public
collection.

Collection PDF export's QR code and the collection page's new "view
publicly" icon (public visibility only, matching the recipe page's same
rule) both now point here instead of the auth-gated /collections/{id}.

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

apps/web/messages/en.json

@@ -531,6 +531,12 @@
     "wantToSaveDescription": "Create a free account to save recipes, scale servings, and build your own library.",
     "getStartedFree": "Get started free"
   },
+  "publicCollection": {
+    "publicCollectionBy": "Public collection by",
+    "viewInLibrary": "View in your library",
+    "wantToSave": "Want to save this collection?",
+    "wantToSaveDescription": "Create a free account to fork collections, save recipes, and build your own library."
+  },
   "substitute": {
     "fetchError": "Couldn't fetch substitutes.",
     "titleFor": "Substitute for {ingredient}",