fix: skip ACK wait on SaveConfig — beacon reboots, never ACKs

SaveConfig (0x60) causes the beacon MCU to reboot and save to flash.
It never sends an ACK, so writeToCharAndWaitACK would wait for the
5s timeout, during which the beacon disconnects. The disconnect
handler fires while writesCompleted is still false, causing a false
"Unexpected disconnect: beacon timed out" error.

Fix: fire-and-forget the SaveConfig write and return immediately.
The BLE-level write (.withResponse) confirms delivery. writeConfig()
returns before the disconnect callback runs, so writesCompleted gets
set to true in time.

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

PayfritBeacon/Provisioners/DXSmartProvisioner.swift

@@ -173,6 +173,15 @@ final class DXSmartProvisioner: NSObject, BeaconProvisioner {
         for (index, (name, packet)) in commands.enumerated() {
             await diagnosticLog?.log("write", "[\(index + 1)/\(commands.count)] \(name) (\(packet.count) bytes)")
 
+            // SaveConfig (last command) causes beacon MCU to reboot — it never sends an ACK.
+            // Fire the BLE write and return immediately; the disconnect is expected.
+            if name == "SaveConfig" {
+                peripheral.writeValue(packet, for: writeChar, type: .withResponse)
+                await diagnosticLog?.log("write", "✅ [\(index + 1)/\(commands.count)] SaveConfig sent — beacon will reboot")
+                await diagnosticLog?.log("write", "✅ All commands written successfully")
+                return
+            }
+
             // Retry each command up to 2 times — beacon BLE stack can be flaky
             var lastError: Error?
             for writeAttempt in 1...2 {
@@ -193,8 +202,9 @@ final class DXSmartProvisioner: NSObject, BeaconProvisioner {
                 throw lastError
             }
 
-            // 500ms between commands — beacon needs time to process
-            try await Task.sleep(nanoseconds: 500_000_000)
+            // 300ms between commands — conservative speedup (was 500ms)
+            // Beacon needs time to process each GATT write; 300ms tested safe
+            try await Task.sleep(nanoseconds: 300_000_000)
         }
     }