Add DM inbox with NIP-04/NIP-17 support and soft delete

Features:
- Full DM inbox UI with conversation list and message view
- Support for both NIP-04 (kind 4) and NIP-17 (kind 14/1059) encryption
- Progressive message decryption with background loading
- Soft delete using kind 30078 Application Specific Data events
- Message selection UI with delete selected/delete all
- Undelete all functionality per conversation
- Jump to newest button with new message counter
- Conversation filtering (all / follows only)
- Per-conversation relay and encryption settings
- New messages indicator on sidebar (clears when inbox viewed)
- Follow indicator on conversation items

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/components/Settings/index.tsx

@@ -64,6 +64,7 @@ import {
   KeyRound,
   LayoutList,
   List,
+  MessageSquare,
   Monitor,
   Moon,
   Palette,
@@ -155,6 +156,9 @@ export default function Settings() {
   // System settings
   const [filterOutOnionRelays, setFilterOutOnionRelays] = useState(storage.getFilterOutOnionRelays())
 
+  // Messaging settings
+  const [preferNip44, setPreferNip44] = useState(storage.getPreferNip44())
+
   const handleLanguageChange = (value: TLanguage) => {
     i18n.changeLanguage(value)
     setLanguage(value)
@@ -528,6 +532,37 @@ export default function Settings() {
           </AccordionItem>
         )}
 
+        {/* Messaging */}
+        {!!pubkey && (
+          <AccordionItem value="messaging">
+            <AccordionTrigger className="px-4 hover:no-underline">
+              <div className="flex items-center gap-4">
+                <MessageSquare className="size-4" />
+                <span>{t('Messaging')}</span>
+              </div>
+            </AccordionTrigger>
+            <AccordionContent className="px-4 space-y-4">
+              <SettingItem>
+                <Label htmlFor="prefer-nip44" className="text-base font-normal">
+                  <div>{t('Prefer NIP-44 encryption')}</div>
+                  <div className="text-muted-foreground text-sm">
+                    {t('Use modern encryption for new conversations')}
+                  </div>
+                </Label>
+                <Switch
+                  id="prefer-nip44"
+                  checked={preferNip44}
+                  onCheckedChange={(checked) => {
+                    storage.setPreferNip44(checked)
+                    setPreferNip44(checked)
+                    dispatchSettingsChanged()
+                  }}
+                />
+              </SettingItem>
+            </AccordionContent>
+          </AccordionItem>
+        )}
+
         {/* System */}
         <AccordionItem value="system">
           <AccordionTrigger className="px-4 hover:no-underline">