feat(desktop): add DM broadcast status banner and audit fixes

- Show relay confirmation URLs in broadcast banner
- Add relayUrls field to DmBroadcastStatus.Sent
- Wire send progress tracking with per-relay confirmations
- Fix empty chatroom Loading state transition
- Improve NewDmDialog npub metadata resolution
- Harden sendAndWaitForResponse timeout handling

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

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/ui/chat/DmBroadcastBanner.kt

@@ -127,6 +127,15 @@ fun DmBroadcastBanner(
                         trackColor = MaterialTheme.colorScheme.surfaceVariant,
                     )
                 }
+
+                if (status is DmBroadcastStatus.Sent && status.relayUrls.isNotEmpty()) {
+                    Text(
+                        text = status.relayUrls.joinToString(", "),
+                        style = MaterialTheme.typography.bodySmall,
+                        color = contentColor.copy(alpha = 0.7f),
+                        modifier = Modifier.padding(start = 28.dp),
+                    )
+                }
             }
         }
     }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/ui/chat/DmBroadcastStatus.kt

@@ -38,6 +38,7 @@ sealed class DmBroadcastStatus {
 
     data class Sent(
         val relayCount: Int,
+        val relayUrls: List<String> = emptyList(),
     ) : DmBroadcastStatus()
 
     data class Failed(