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/src/dminvitedialog.cpp

@@ -89,7 +89,7 @@ void DmInviteDialog::sendInvite() {
 }
 
 void DmInviteDialog::onResult(const uint8_t* data, int len) {
-    if (!data || len != 28) { GUI_ERROR("invite PM: invalid result bytes=%d", len); return; }
+    if (!data || len != 36) { GUI_ERROR("invite PM: invalid result bytes=%d", len); return; }
     uint64_t request, peer, conv; int32_t result;
     memcpy(&request, data, 8); memcpy(&result, data + 8, 4);
     memcpy(&peer, data + 12, 8); memcpy(&conv, data + 20, 8);