fix: update compose submodule to pick up backup network fix

The backup_stack.service was failing because the deployed compose.yml
still had backup_net declared as external: true, but the network was
never created externally.

PR #45 on the compose repo (d7449e9) already fixed this by changing
to driver: bridge, but the infra submodule was still pinned to a
pre-fix commit.

This updates assets/compose to d7449e9 so the next nixos-rebuild
switch deploys the fix.

hosts/lazyworkhorse/configuration.nix

@@ -207,6 +207,7 @@
     ai = {
       path = self + "/assets/compose/ai";
       envFile = config.age.secrets.containers_env.path;
+      ports = [ 22000 ];  # Syncthing TCP sync
     };
 
     cloudstorage = {
@@ -474,7 +475,7 @@
   services.openssh.settings = {
     PermitRootLogin = "no";
     MaxAuthTries = 3;
-    MaxSessions = 10;
+    MaxSessions = 20;
     LoginGraceTime = 30;
     ClientAliveInterval = 300;
     ClientAliveCountMax = 2;