Reduce test-process churn to fix flaky CI exit hang

The app test job intermittently hung at process exit. The suite is
load-sensitive and historically prone to cooperative-pool/teardown
deadlocks; the security changes added background work to the test process
that pushed it over the edge. Make the unit-test BLEService/identity
manager quiescent and remove blocking sync:

- forceSave() no longer does queue.sync(.barrier). It is reachable from
  deinit and from async tests on the swift-concurrency cooperative pool,
  where a blocking barrier-sync can starve/deadlock the pool. It now
  cancels the debounce timer and persists directly. (Removed the
  now-unneeded queue-specific-key re-entrancy machinery.)
- SecureIdentityStateManager persists synchronously under tests instead of
  scheduling a DispatchSourceTimer that lingers past process exit.
- Gate gossip-sync start (in addition to the maintenance timer) behind
  real Bluetooth init, so the test BLEService runs no periodic
  sign/broadcast/sync churn.
- Skip the panic Nostr reconnect under tests (connecting the shared relay
  singleton starts network/reconnect work that never completes).

Production behavior is unchanged: real Bluetooth builds run all timers and
the debounced save as before; the debounce save now actually fires
(previously a Timer on a GCD queue that never ran).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

bitchat/Services/BLE/BLEService.swift

@@ -136,10 +136,12 @@ final class BLEService: NSObject {
     private var maintenanceTimer: DispatchSourceTimer?  // Single timer for all maintenance tasks
     private var maintenanceCounter = 0  // Track maintenance cycles
     /// Whether real CoreBluetooth managers were initialized. When false (unit
-    /// tests), the periodic maintenance timer is not started: it only drains BLE
-    /// writes/notifications and re-announces, which is meaningless without
-    /// Bluetooth and would otherwise run its cross-queue work in-process.
-    private var maintenanceTimerEnabled = false
+    /// tests), periodic mesh background work is not started — the maintenance
+    /// timer and the gossip-sync timers only drain BLE writes/notifications,
+    /// re-announce, and sign/broadcast sync packets, all meaningless without
+    /// Bluetooth. Leaving them running in the test process is pure background
+    /// churn that aggravates flaky exit hangs.
+    private var meshBackgroundEnabled = false
 
     // MARK: - Connection budget & scheduling (central role)
     private var connectionScheduler = BLEConnectionScheduler<CBPeripheral>()
@@ -240,7 +242,7 @@ final class BLEService: NSObject {
         
         // Single maintenance timer for all periodic tasks (dispatch-based for
         // determinism). Only run it when real Bluetooth managers exist.
-        maintenanceTimerEnabled = initializeBluetoothManagers
+        meshBackgroundEnabled = initializeBluetoothManagers
         startMaintenanceTimer()
 
         // Publish initial empty state
@@ -271,7 +273,12 @@ final class BLEService: NSObject {
         
         let manager = GossipSyncManager(myPeerID: myPeerID, config: config, requestSyncManager: requestSyncManager)
         manager.delegate = self
-        manager.start()
+        // Only start the periodic sync timers when real Bluetooth exists. In unit
+        // tests there is no mesh to sync with, and the periodic sign/broadcast
+        // churn just keeps the process busy and aggravates flaky exit hangs.
+        if meshBackgroundEnabled {
+            manager.start()
+        }
         gossipSyncManager = manager
     }
 
@@ -439,7 +446,7 @@ final class BLEService: NSObject {
     /// `startServices()` — the latter matters after a panic reset, where
     /// `stopServices()` cancels and nils the timer.
     private func startMaintenanceTimer() {
-        guard maintenanceTimerEnabled, maintenanceTimer == nil else { return }
+        guard meshBackgroundEnabled, maintenanceTimer == nil else { return }
         let timer = DispatchSource.makeTimerSource(queue: bleQueue)
         timer.schedule(deadline: .now() + TransportConfig.bleMaintenanceInterval,
                        repeating: TransportConfig.bleMaintenanceInterval,