fix: prevent DXSmart disconnect race killing the "Write Config" screen

After DXSmart auth completes, the beacon often drops BLE connection
due to aggressive timeouts. The disconnect handler was treating this
as a failure, stomping the .connected state before the user could see
the "Write Config" button.

Changes:
- Ignore BLE disconnects during .connected state for DXSmart beacons
  (the LED keeps flashing regardless of BLE connection)
- Auto-reconnect in writeConfigToConnectedBeacon() if BLE dropped
  while waiting for user confirmation

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

PayfritBeacon/Views/ScanView.swift

@@ -634,9 +634,15 @@ struct ScanView: View {
                     Task { @MainActor [weak self] in
                         let reason = error?.localizedDescription ?? "beacon timed out"
                         provisionLog?.log("disconnect", "Unexpected disconnect: \(reason)", isError: true)
-                        // If we're in any active provisioning state, show failure
+                        guard let self = self else { return }
-                        if let self = self,
+                        // DXSmart: disconnect during .connected is expected — beacon keeps
-                           self.provisioningState == .connecting || self.provisioningState == .connected ||
+                        // flashing after BLE drops. We'll reconnect when user taps Write Config.
+                        if self.provisioningState == .connected && beacon.type == .dxsmart {
+                            provisionLog?.log("disconnect", "DXSmart idle disconnect — beacon still flashing, ignoring")
+                            return
+                        }
+                        // For all other active states, treat disconnect as failure
+                        if self.provisioningState == .connecting || self.provisioningState == .connected ||
                            self.provisioningState == .writing || self.provisioningState == .verifying {
                             self.provisioningState = .failed
                             self.errorMessage = "Beacon disconnected: \(reason)"
@@ -718,6 +724,15 @@ struct ScanView: View {
         statusMessage = "Writing config to DX-Smart…"
 
         do {
+            // Reconnect if the beacon dropped BLE during the "confirm flashing" wait
+            if !provisioner.isConnected {
+                provisionLog.log("write", "Beacon disconnected while waiting — reconnecting…")
+                statusMessage = "Reconnecting to beacon…"
+                try await provisioner.connect()
+                provisionLog.log("write", "Reconnected — writing config…")
+                statusMessage = "Writing config to DX-Smart…"
+            }
+
             try await provisioner.writeConfig(config)
             provisioner.disconnect()