Add NRC (Nostr Relay Connect) for cross-device sync

Implements NRC listener that allows other user clients to connect
and sync events through a rendezvous relay. Features:
- REQ-only (read) sync for security
- Secret-based and CAT token authentication
- NIP-44 encrypted tunneling
- Device-specific event filtering via d-tag prefix
- Session management with timeouts
- Settings UI with QR code connection flow

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/components/Settings/index.tsx

@@ -6,6 +6,7 @@ import EmojiPackList from '@/components/EmojiPackList'
 import EmojiPickerDialog from '@/components/EmojiPickerDialog'
 import FavoriteRelaysSetting from '@/components/FavoriteRelaysSetting'
 import MailboxSetting from '@/components/MailboxSetting'
+import NRCSettings from '@/components/NRCSettings'
 import NoteList from '@/components/NoteList'
 import Tabs from '@/components/Tabs'
 import {
@@ -73,6 +74,7 @@ import {
   PencilLine,
   RotateCcw,
   ScanLine,
+  RefreshCw,
   Server,
   Settings2,
   Smile,
@@ -105,7 +107,7 @@ const NOTIFICATION_STYLES = [
 ] as const
 
 // Accordion item values for keyboard navigation
-const ACCORDION_ITEMS = ['general', 'appearance', 'relays', 'wallet', 'posts', 'emoji-packs', 'messaging', 'system']
+const ACCORDION_ITEMS = ['general', 'appearance', 'relays', 'sync', 'wallet', 'posts', 'emoji-packs', 'messaging', 'system']
 
 export default function Settings() {
   const { t, i18n } = useTranslation()
@@ -123,7 +125,7 @@ export default function Settings() {
   // Get the visible accordion items based on pubkey availability
   const visibleAccordionItems = pubkey
     ? ACCORDION_ITEMS
-    : ACCORDION_ITEMS.filter((item) => !['wallet', 'posts', 'emoji-packs', 'messaging'].includes(item))
+    : ACCORDION_ITEMS.filter((item) => !['sync', 'wallet', 'posts', 'emoji-packs', 'messaging'].includes(item))
 
   // Register as a navigation region - Settings decides what "up/down" means
   const handleSettingsIntent = useCallback(
@@ -548,6 +550,23 @@ export default function Settings() {
           </AccordionItem>
         </NavigableAccordionItem>
 
+        {/* Sync (NRC) */}
+        {!!pubkey && (
+          <NavigableAccordionItem ref={setAccordionRef('sync')} isSelected={isAccordionSelected('sync')}>
+            <AccordionItem value="sync">
+            <AccordionTrigger className="px-4 hover:no-underline">
+              <div className="flex items-center gap-4">
+                <RefreshCw className="size-4" />
+                <span>{t('Device Sync')}</span>
+              </div>
+            </AccordionTrigger>
+            <AccordionContent className="px-4">
+              <NRCSettings />
+            </AccordionContent>
+            </AccordionItem>
+          </NavigableAccordionItem>
+        )}
+
         {/* Wallet */}
         {!!pubkey && (
           <NavigableAccordionItem ref={setAccordionRef('wallet')} isSelected={isAccordionSelected('wallet')}>