chat_core: call ensure_channel_ready on invite — create msg/peers tables + register in db_sync

Without this, invite creates the channel in SQLite but db_sync never
knows about it, so peer sync fails with 'instance NOT FOUND'.

tools/chatgui/transport/chat_core.c

@@ -634,6 +634,9 @@ void chat_core_connect_from_invite(struct chat_invite* inv) {
     DEBUG_INFO(DEBUG_CATEGORY_CONNECTIVITY, "%s: invite saved node=0x%016llx addrs=%d, starting direct connect",
                CC_ID, (unsigned long long)node_id, inv->addr_count);
 
+    { char ch_str[32]; snprintf(ch_str, sizeof(ch_str), "%llu", (unsigned long long)inv->channel_id);
+      chat_core_ensure_channel_ready(ch_str); }
+
     chat_core_connect_auto(node_id, connect_result_cb, &inv->channel_id, NULL);
 }