Refactor Zed/Flatpak options and add C++ & clangd settings

- Switch Zed remote server and Flatpak packages to use `enable`
suboption - Update host modules to match the new option hierarchy - Add
default C++ settings (format on save, tab size) to Zed user settings -
Introduce clangd LSP configuration with inlay hints and fallback command

hosts/default/system-modules.nix

@@ -6,9 +6,9 @@ _: {
   flatpak = {
     enable = true; # Flatpak: universal packaging system for Linux
     packages = {
-      sober = false; # Roblox client
-      warehouse = true; # Flatpak manager
-      flatseal = true; # Flatpak permissions manager
+      sober.enable = false; # Roblox client
+      warehouse.enable = true; # Flatpak manager
+      flatseal.enable = true; # Flatpak permissions manager
     };
   };