Add agenix-rekey module + rekey config back to lazyworkhorse

agenix-rekey auto-re-encrypts secrets per host at build time:
- Encrypted once in git with master identity
- Re-encrypted for each host using their SSH host key
- No manual multi-recipient encryption needed

flake.nix

@@ -262,6 +262,7 @@
             }
             inputs.home-manager.nixosModules.home-manager
             agenix.nixosModules.default
+            agenix-rekey.nixosModules.default
             ./hosts/lazyworkhorse/configuration.nix
             ./hosts/lazyworkhorse/hardware-configuration.nix
             ./modules/nixos/filesystem/hoardingcow-mount.nix

hosts/lazyworkhorse/configuration.nix

@@ -589,3 +589,9 @@
 
 
 }
+  # agenix-rekey — automatic re-encryption for each target host
+  age.rekey = {
+    masterIdentities = [
+      "/home/gortium/.ssh/gortium_ssh_key"
+    ];
+  };

secrets/secrets.nix

@@ -12,5 +12,7 @@ in
   "home_wifi.age".publicKeys = authorizedKeys;
   "lazyworkhorse_host_ssh_key.age".publicKeys = authorizedKeys;
   "n8n_ssh_key.age".publicKeys = authorizedKeys;
-  "builder_key.age".publicKeys = authorizedKeys;
+"builder_key.age".publicKeys = authorizedKeys ++ [
+    keys.hosts.uConsole.bootstrap
+  ];
 }