fix(qr): guest menu 500 (SSR) + remove café discovery from owner panel

1. The /q/{code} guest menu returned HTTP 500 on every load. Root cause:
   menu-item-model-viewer.tsx did a top-level `import "@google/model-viewer"`,
   a browser-only lib that touches `self` at module evaluation. Next pulled
   it into the server module graph (page → qr-guest-menu → qr-menu-3d-sheet →
   model-viewer) and SSR crashed with "self is not defined". Now the library
   is imported lazily inside useEffect (client-only); a poster placeholder
   shows until the custom element registers. Verified /q/* now returns 200.

2. Removed the "discover" (browse other cafés) item from the café owner
   sidebar — café discovery belongs in Koja, not the owner panel. The owner
   still manages their OWN Koja listing from Settings.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/dashboard/src/components/menu/menu-item-model-viewer.tsx

@@ -1,6 +1,6 @@
 "use client";
 
-import "@google/model-viewer";
+import { useEffect, useState } from "react";
 import { resolveMediaUrl } from "@/lib/api/client";
 
 type MenuItemModelViewerProps = {
@@ -10,16 +10,60 @@ type MenuItemModelViewerProps = {
   className?: string;
 };
 
+// `@google/model-viewer` references browser globals (`self`) at module load, so a
+// top-level `import` crashes server-side rendering (e.g. the /q guest menu).
+// Load it lazily on the client only, once, the first time a viewer mounts.
+let modelViewerLoad: Promise<unknown> | null = null;
+function ensureModelViewerLoaded(): Promise<unknown> {
+  if (typeof window === "undefined") return Promise.resolve();
+  modelViewerLoad ??= import("@google/model-viewer");
+  return modelViewerLoad;
+}
+
 export function MenuItemModelViewer({
   modelUrl,
   posterUrl,
   alt,
   className,
 }: MenuItemModelViewerProps) {
+  const [ready, setReady] = useState(false);
+
+  useEffect(() => {
+    let active = true;
+    void ensureModelViewerLoaded().then(() => {
+      if (active) setReady(true);
+    });
+    return () => {
+      active = false;
+    };
+  }, []);
+
   const src = resolveMediaUrl(modelUrl);
   const poster = posterUrl ? resolveMediaUrl(posterUrl) : undefined;
   if (!src) return null;
 
+  // Until the custom element is registered, show the poster (or an empty box) so
+  // layout is stable and nothing references the browser-only library on the server.
+  if (!ready) {
+    return (
+      <div
+        className={className}
+        style={{
+          width: "100%",
+          height: "100%",
+          minHeight: "min(72vh, 420px)",
+          backgroundColor: "rgba(0,0,0,0.04)",
+          backgroundImage: poster ? `url(${poster})` : undefined,
+          backgroundSize: "contain",
+          backgroundPosition: "center",
+          backgroundRepeat: "no-repeat",
+        }}
+        aria-label={alt}
+        role="img"
+      />
+    );
+  }
+
   return (
     // @ts-expect-error model-viewer is a custom element from @google/model-viewer
     <model-viewer

web/dashboard/src/lib/sidebar-nav.ts

@@ -21,7 +21,6 @@ import {
   Wallet,
   Clock,
   LifeBuoy,
-  Compass,
 } from "lucide-react";
 
 export type NavGroupId = "main" | "customers" | "management";
@@ -39,7 +38,6 @@ export type NavItemKey =
   | "coupons"
   | "sms"
   | "reviews"
-  | "discover"
   | "inventory"
   | "expenses"
   | "shifts"
@@ -93,7 +91,8 @@ export const NAV_GROUPS: NavGroupDef[] = [
       { key: "coupons", href: "/coupons", icon: Ticket },
       { key: "sms", href: "/sms", icon: MessageSquare },
       { key: "reviews", href: "/reviews", icon: Star },
-      { key: "discover", href: "/discover", icon: Compass },
+      // NOTE: café discovery (browsing other cafés) lives in Koja, not the owner
+      // panel. The owner manages their OWN Koja listing from Settings.
     ],
   },
   {