feat: direct messages

1:1 conversations (userAId < userBId dedup pair), messages,
per-participant read tracking (conversation_reads). Block relationship
is enforced on every send. UI: /messages list + /messages/[id] thread
(5s poll), MessageButton on profiles, unread-badged nav icon.

This completes the social-feature backlog: notifications, rate
limiting, blocking, reporting, search/discovery, mentions, DMs, plus
fixes for the recipe-visibility 404, follow race, and 2-level comment
thread cap found during the earlier audit.

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

apps/web/app/(app)/messages/page.tsx

@@ -0,0 +1,21 @@
+import type { Metadata } from "next";
+import { MessageCircle } from "lucide-react";
+import { ConversationsList } from "@/components/social/conversations-list";
+
+export const metadata: Metadata = { title: "Messages — Epicure" };
+
+export default function MessagesPage() {
+  return (
+    <div className="max-w-5xl mx-auto h-[calc(100vh-8rem)] border rounded-xl overflow-hidden flex">
+      <div className="w-full sm:w-80 border-r shrink-0 overflow-y-auto">
+        <ConversationsList />
+      </div>
+      <div className="hidden sm:flex flex-1 items-center justify-center text-muted-foreground">
+        <div className="text-center space-y-2">
+          <MessageCircle className="h-10 w-10 mx-auto opacity-50" />
+          <p className="text-sm">Select a conversation</p>
+        </div>
+      </div>
+    </div>
+  );
+}