android: DiagLog thread-safe timestamps; auto-connect survives stop/start

- SimpleDateFormat is now used under the lock; rotation counts bytes
- AutoConnectManager.stop() clears pendingEvaluate, whose reset runnable
  it removes, so later connects are not silently swallowed

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/frontends/android/app/src/main/java/org/strongswan/android/logic/DiagLog.kt

@@ -62,9 +62,10 @@ object DiagLog
 		val base = dir ?: return
 		try
 		{
-			val line = "${format.format(Date())} $tag: $message\n"
 			synchronized(this)
 			{
+				/* SimpleDateFormat is not thread-safe: format under the lock */
+				val line = "${format.format(Date())} $tag: $message\n"
 				if (written > MAX_SIZE)
 				{
 					rotate(base)
@@ -79,7 +80,7 @@ object DiagLog
 				}
 				w.write(line)
 				w.flush()
-				written += line.length + 1
+				written += line.toByteArray(Charsets.UTF_8).size
 			}
 		}
 		catch (_: Exception)

src/frontends/android/app/src/main/java/org/strongswan/android/logic/autoconnect/AutoConnectManager.kt

@@ -145,6 +145,9 @@ class AutoConnectManager private constructor(
 			return
 		}
 		handler.removeCallbacksAndMessages(null)
+		/* the runnable that clears this flag was just removed with the
+		 * callbacks: clear it here or every later connect is swallowed */
+		pendingEvaluate.set(false)
 		service?.unregisterListener(this)
 		try
 		{