fix(nip46): fix bunker decrypt/encrypt response parsing and increase timeout

Two issues fixed:

1. BunkerResponseDeserializer produces generic BunkerResponse for decrypt/encrypt
   results (plain strings that aren't pubkeys or JSON). The response parsers only
   matched typed subtypes (BunkerResponseDecrypt/Encrypt), causing all decrypt and
   encrypt operations through NIP-46 bunker to fail with ReceivedButCouldNotPerform.
   Fix: parsers now fall back to extracting response.result directly.

2. RemoteSignerManager timeout was 30s, shorter than Amber's 60s approval window.
   Fix: increased to 65s with safe retry (republishes same request, preserving UUID
   so bunker responses always match).

3. Desktop ChatPane showed raw ciphertext on decrypt failure instead of an error
   message. Fix: shows "Could not decrypt the message" in italic.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/chats/ChatPane.kt

@@ -455,7 +455,7 @@ private fun MessageWithReactions(
                     try {
                         event.decryptContent(account.signer)
                     } catch (_: Exception) {
-                        event.content
+                        null
                     }
                 }
 
@@ -597,11 +597,22 @@ private fun MessageWithReactions(
 
                     else -> {
                         SelectionContainer {
-                            Text(
-                                text = decryptedContent ?: "",
-                                style = MaterialTheme.typography.bodyMedium,
-                                color = MaterialTheme.colorScheme.onSurface,
-                            )
+                            if (decryptedContent != null) {
+                                Text(
+                                    text = decryptedContent!!,
+                                    style = MaterialTheme.typography.bodyMedium,
+                                    color = MaterialTheme.colorScheme.onSurface,
+                                )
+                            } else {
+                                Text(
+                                    text = "Could not decrypt the message",
+                                    style =
+                                        MaterialTheme.typography.bodyMedium.copy(
+                                            fontStyle = androidx.compose.ui.text.font.FontStyle.Italic,
+                                        ),
+                                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                                )
+                            }
                         }
                     }
                 }