feat(minion): enable flatpak

I have some apps that I want to install via flatpak, so let's get and
persist flatpak :)

packetmix/homes/minion/flatpak.nix

···
+{  
+  clicks.storage.impermanence.persist.directories = [ ".var/app" ".local/share/flatpak" ];
+}

packetmix/systems/minion/flatpak.nix

···
+{
+  services.flatpak.enable = true;
+
+  clicks.storage.impermanence.persist.directories = [
+    "/var/lib/flatpak"
+  ];
+}