backwards/pinwheel: Add SSH key for backwards to access pinwheel

Pinwheel's sshd had no way to accept keys from other hosts. Give it the
same `authorizedKeysCommand` setup as backwards and manatee, and authorize
a new `alex.backwards-pinwheel` key that backwards uses for `ssh pinwheel`.

hosts/backwards/modules/ssh/default.nix

@@ -31,6 +31,13 @@ in
             Port = 1122;
           };
 
+          "pinwheel" = {
+            HostName = "pinwheel";
+            User = "alex";
+            IdentityFile = "/home/alex/.ssh/alex.backwards-pinwheel";
+            Port = 1122;
+          };
+
           "git.ppp.pm" = {
             HostName = "git.ppp.pm";
             IdentityFile = "/home/alex/.ssh/alex.backwards-git.ppp.pm";
@@ -115,6 +122,19 @@ in
         group = "users";
       };
 
+      "alex.backwards-pinwheel" = {
+        file = ../../../../secrets/backwards/alex.backwards-pinwheel.age;
+        path = "/home/alex/.ssh/alex.backwards-pinwheel";
+        owner = "alex";
+        group = "users";
+      };
+      "alex.backwards-pinwheel.pub" = {
+        file = ../../../../secrets/backwards/alex.backwards-pinwheel.pub.age;
+        path = "/home/alex/.ssh/alex.backwards-pinwheel.pub";
+        owner = "alex";
+        group = "users";
+      };
+
       "alex.pinwheel-backwards.pub" = {
         file = ../../../../secrets/pinwheel/alex.pinwheel-backwards.pub.age;
         path = "${authorizedKeysPath}/alex.pinwheel-backwards.pub";