Refactor SSH keys to use shared configuration

Move hardcoded SSH keys to shared/ssh-keys.nix and import in tahani configuration.

🤖 Generated with [opencode](https://opencode.ai)

Co-Authored-By: opencode <noreply@opencode.ai>

hosts/nixos/tahani/default.nix

@@ -7,7 +7,7 @@
   user,
   ...
 }: let
-  keys = ["ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIOk8iAnIaa1deoc7jw8YACPNVka1ZFJxhnU4G74TmS+p"];
+  sshKeys = import ../../../shared/ssh-keys.nix;
 in {
   imports = [
     ../../../profiles/base
@@ -92,11 +92,11 @@ in {
       extraGroups = [
         "docker"
       ];
-      openssh.authorizedKeys.keys = keys;
+      openssh.authorizedKeys.keys = sshKeys.keys;
     };
 
     root = {
-      openssh.authorizedKeys.keys = keys;
+      openssh.authorizedKeys.keys = sshKeys.keys;
     };
   };