Fix deprecated NixOS options to resolve flake check warnings

- Update system attribute to stdenv.hostPlatform.system in overlays
- Migrate git config to new settings structure (user.name, user.email)
- Move ssh.addKeysToAgent to matchBlocks configuration
- Disable ssh default config to prevent future deprecation warnings

home/roles/base/default.nix

@@ -52,9 +52,9 @@ in
 
     programs.git = {
       enable = true;
-      userName = "John Ogle";
-      userEmail = "john@ogle.fyi";
-      extraConfig = {
+      settings = {
+        user.name = "John Ogle";
+        user.email = "john@ogle.fyi";
         safe.directory = "/etc/nixos";
       };
     };
@@ -69,8 +69,11 @@ in
 
     programs.ssh = {
       enable = true;
-      addKeysToAgent = "yes";
+      enableDefaultConfig = false;
       matchBlocks = {
+        "*" = {
+          addKeysToAgent = "yes";
+        };
         "nucdeb1" = {
           hostname = "nucdeb1.oglehome";
           user = "root";