fix(security): newline-terminate managed authorized_keys files

Both managed authorized_keys files lacked a trailing newline. sshd reads
the final key fine on its own, but any subsequent append (tooling, a
follow-up key, or the validation harness) concatenated onto the last key
line, fusing two keys into one unparseable blob and silently breaking
public-key auth for both.

Add the trailing newline so the files concatenate safely.

🤖 Generated with [Crush](https://github.com/charmassociates/crush)

Assisted-by: GLM-5 via Crush <crush@charm.land>

ProjectCode/ConfigFiles/SSH/AuthorizedKeys/localuser-ssh-authorized-keys

@@ -1,2 +1,2 @@
 ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIDHaBNuLS+GYGRPc9wne63Ocr+R+/Q01Y9V0FTv0RnG3
-ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIPyMR0lFgiMKhQJ5aqy68nR0BQp1cNzi/wIThyuTV4a8 tsyscto@ultix-control
+ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIPyMR0lFgiMKhQJ5aqy68nR0BQp1cNzi/wIThyuTV4a8 tsyscto@ultix-control

ProjectCode/ConfigFiles/SSH/AuthorizedKeys/root-ssh-authorized-keys

@@ -1,2 +1,2 @@
 ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIDHaBNuLS+GYGRPc9wne63Ocr+R+/Q01Y9V0FTv0RnG3
-ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIPyMR0lFgiMKhQJ5aqy68nR0BQp1cNzi/wIThyuTV4a8 tsyscto@ultix-control
+ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIPyMR0lFgiMKhQJ5aqy68nR0BQp1cNzi/wIThyuTV4a8 tsyscto@ultix-control