perf(bundle): lazy on-demand modals in Layout; skip the Cashu chunk without a wallet

- BackupReminder, CustomizeNavSheet, SetStatusDialog and LoginDialog are only
  needed after the user acts -> React.lazy (Layout chunk 511 KB -> 486 KB)
- The Cashu balance widget now only mounts when a wallet likely exists (web:
  localStorage hint; native: always, since the seed is in the KeyStore), so
  wallet-less visitors never download the 245 KB Cashu chunk

src/components/Layout.tsx

@@ -2,7 +2,7 @@ import { useState, useRef, lazy, Suspense } from 'react';
 import { Link, useLocation } from 'react-router-dom';
 import { nip19 } from 'nostr-tools';
 import { cn } from '@/lib/utils';
-import { CustomizeNavSheet } from '@/components/CustomizeNavSheet';
+import { isNativePlatform } from '@/lib/platform';
 import { useNavPreferences, useDesktopNavPreferences, type NavTab } from '@/hooks/useNavPreferences';
 import { Button } from '@/components/ui/button';
 import { Badge } from '@/components/ui/badge';
@@ -15,9 +15,7 @@ import {
   DropdownMenuSeparator,
 } from '@/components/ui/dropdown-menu';
 import { LoginArea } from '@/components/auth/LoginArea';
-import { LoginDialog } from '@/components/auth/LoginDialog';
 import { useSasquatchGuide } from '@/hooks/useSasquatchGuide';
-import { BackupReminder } from '@/components/BackupReminder';
 import { LanguageToggle } from '@/components/LanguageToggle';
 import { useCurrentUser } from '@/hooks/useCurrentUser';
 import { useTranslation } from '@/contexts/LanguageContext';
@@ -54,7 +52,6 @@ import {
 } from 'lucide-react';
 import { OfflineIndicator } from '@/components/OfflineIndicator';
 import { UserStatusIndicator } from '@/components/UserStatusIndicator';
-import { SetStatusDialog } from '@/components/SetStatusDialog';
 import { Avatar, AvatarImage, AvatarFallback } from '@/components/ui/avatar';
 import { useAuthor } from '@/hooks/useAuthor';
 import { genUserName } from '@/lib/genUserName';
@@ -76,6 +73,35 @@ const LazyCashuMenuBalance = lazy(() =>
 const LazySasquatchGuide = lazy(() =>
   import('@/components/SasquatchGuide').then((m) => ({ default: m.SasquatchGuide })),
 );
+// On-demand modals — only rendered after the user opens them, so keep them out
+// of the always-loaded Layout chunk.
+const LazyCustomizeNavSheet = lazy(() =>
+  import('@/components/CustomizeNavSheet').then((m) => ({ default: m.CustomizeNavSheet })),
+);
+const LazySetStatusDialog = lazy(() =>
+  import('@/components/SetStatusDialog').then((m) => ({ default: m.SetStatusDialog })),
+);
+const LazyLoginDialog = lazy(() =>
+  import('@/components/auth/LoginDialog').then((m) => ({ default: m.LoginDialog })),
+);
+const LazyBackupReminder = lazy(() =>
+  import('@/components/BackupReminder').then((m) => ({ default: m.BackupReminder })),
+);
+
+/**
+ * Cheap synchronous hint that a Cashu wallet MIGHT exist, used to decide
+ * whether to even load the (large) wallet chunk. On native the seed lives in
+ * the OS KeyStore which we can't query synchronously, so we always load there;
+ * on web `useCashu` persists the mnemonic in localStorage under this key.
+ */
+function hasCashuWalletHint(): boolean {
+  if (isNativePlatform()) return true;
+  try {
+    return !!localStorage.getItem('cashu-mnemonic');
+  } catch {
+    return false;
+  }
+}
 
 interface LayoutProps {
   children: React.ReactNode;
@@ -371,9 +397,11 @@ function MobileNav({
           {isWallet ? (
             <>
               <Wallet className={cn('h-[22px] w-[22px] transition-transform duration-300', active ? 'scale-110' : 'group-active:scale-95')} />
-              <Suspense fallback={null}>
-                <LazyCashuBalanceBadge />
-              </Suspense>
+              {hasCashuWalletHint() && (
+                <Suspense fallback={null}>
+                  <LazyCashuBalanceBadge />
+                </Suspense>
+              )}
             </>
           ) : (
             <tab.icon className={cn('h-[22px] w-[22px] transition-transform duration-300', active ? 'scale-110' : 'group-active:scale-95')} />
@@ -657,9 +685,11 @@ export function Layout({ children, noPadding }: LayoutProps) {
                   )}
                 >
                   <Wallet className="h-5 w-5" />
-                  <Suspense fallback={null}>
-                    <LazyCashuBalanceText />
-                  </Suspense>
+                  {hasCashuWalletHint() && (
+                    <Suspense fallback={null}>
+                      <LazyCashuBalanceText />
+                    </Suspense>
+                  )}
                 </Button>
               </Link>
             )}
@@ -778,9 +808,11 @@ export function Layout({ children, noPadding }: LayoutProps) {
                               <p className="text-xs text-muted-foreground">Ecash</p>
                             </div>
                           </div>
-                          <Suspense fallback={null}>
-                            <LazyCashuMenuBalance />
-                          </Suspense>
+                          {hasCashuWalletHint() && (
+                            <Suspense fallback={null}>
+                              <LazyCashuMenuBalance />
+                            </Suspense>
+                          )}
                         </div>
                       </div>
                     </Link>
@@ -973,8 +1005,10 @@ export function Layout({ children, noPadding }: LayoutProps) {
         </div>
       </header>
 
-      {/* Backup Reminder */}
-      <BackupReminder />
+      {/* Backup Reminder — lazy (on-demand banner) */}
+      <Suspense fallback={null}>
+        <LazyBackupReminder />
+      </Suspense>
 
       {/* Main Content — extra bottom padding on mobile so the fixed bottom nav never overlaps */}
       {/* noPadding: full-bleed pages (map) manage their own height */}
@@ -1048,8 +1082,10 @@ export function Layout({ children, noPadding }: LayoutProps) {
         middleTabs={middleTabs}
       />
 
-      {/* Bottom-nav customization sheet (mobile) */}
-      <CustomizeNavSheet open={showCustomizeNav} onOpenChange={setShowCustomizeNav} />
+      {/* Bottom-nav customization sheet (mobile) — lazy (on-demand modal) */}
+      <Suspense fallback={null}>
+        <LazyCustomizeNavSheet open={showCustomizeNav} onOpenChange={setShowCustomizeNav} />
+      </Suspense>
 
       {/* Sasquatch Guide (all screens) — lazy; not needed at first paint */}
       <Suspense fallback={null}>
@@ -1059,18 +1095,22 @@ export function Layout({ children, noPadding }: LayoutProps) {
         />
       </Suspense>
 
-      {/* Set Status Dialog */}
-      <SetStatusDialog
-        open={showStatusDialog}
-        onOpenChange={setShowStatusDialog}
-      />
+      {/* Set Status Dialog — lazy (on-demand modal) */}
+      <Suspense fallback={null}>
+        <LazySetStatusDialog
+          open={showStatusDialog}
+          onOpenChange={setShowStatusDialog}
+        />
+      </Suspense>
 
-      {/* Add-another-account (multi-account switch on mobile) */}
-      <LoginDialog
-        isOpen={showAddAccount}
-        onClose={() => setShowAddAccount(false)}
-        onLogin={() => setShowAddAccount(false)}
-      />
+      {/* Add-another-account (multi-account switch on mobile) — lazy */}
+      <Suspense fallback={null}>
+        <LazyLoginDialog
+          isOpen={showAddAccount}
+          onClose={() => setShowAddAccount(false)}
+          onLogin={() => setShowAddAccount(false)}
+        />
+      </Suspense>
 
       {/* Newsletter: floating pill + Monday admin reminder */}
       <NewsletterOverlay />