feat(chat): add local DM deletion and improve Android member list

Delete local conversations atomically, retain replay protection and sequence counters, and guard asynchronous media work by history generation. Add Android avatar menu and confirmation, persistent file cleanup, and regression coverage.

Fix unnamed member wire padding and compact Android member action spacing.

Validation: 158 core tests passed; targeted DM tests, desktop build, Android unit tests and debug APK build passed.

tools/chatgui-android/app/src/test/java/com/utun/chat/data/MemberAvatarTest.kt

@@ -6,6 +6,20 @@ import java.nio.ByteBuffer
 import java.nio.ByteOrder
 
 class MemberAvatarTest {
+    @Test fun snapshotStringsStopAtFirstNullBeforeDirtyPadding() {
+        for (name in listOf("", "0x06B9", "Без имени", "x".repeat(63))) {
+            val bytes = ByteArray(MEMBER_WIRE_SIZE)
+            bytes.fill(0xff.toByte(), 15, 79)
+            val encoded = name.toByteArray(Charsets.UTF_8)
+            encoded.copyInto(bytes, 15); bytes[15 + encoded.size] = 0
+            ByteBuffer.wrap(bytes).order(ByteOrder.LITTLE_ENDIAN).putLong(79, 456)
+            bytes.fill(0xff.toByte(), 87, 157); bytes[87] = 0; bytes[157] = 1
+            val member = requireNotNull(parseMemberWire(bytes)).toChatMember()
+            assertEquals(name, member.name)
+            assertEquals(456L, member.avatarServer); assertEquals("", member.avatarFile); assertTrue(member.storageRole)
+        }
+    }
+
     @Test fun sharedSnapshotKeepsAvatarAndSignedStorageRole() {
         val bytes = ByteArray(158)
         val b = ByteBuffer.wrap(bytes).order(ByteOrder.LITTLE_ENDIAN)