fix: DM preview shows message body for E2EE rooms; filter inputs match members panel style

- RoomNavItem: change isEncrypted() to isDecryptionFailure() so DM
  previews show actual message body for successfully decrypted E2EE
  events instead of always showing 'Encrypted message'
- Home.tsx / Direct.tsx: upgrade filter inputs to size 400 / radii 400
  with search icon prefix to match the members list search bar style

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/features/room-nav/RoomNavItem.tsx

@@ -454,7 +454,7 @@ function RoomNavItem_({
     // Skip pure membership events
     if (type === StateEvent.RoomMember) return null;
     let body: string;
-    if (latestEvent.isEncrypted()) {
+    if (latestEvent.isDecryptionFailure()) {
       body = 'Encrypted message';
     } else if (type === MessageEvent.Sticker) {
       body = 'Sticker';