feat: add support for selecting additional SSH keys from Hetzner in server creation form

tests/Feature/HetznerServerCreationTest.php

@@ -0,0 +1,49 @@
+<?php
+
+// Note: Full Livewire integration tests require database setup
+// These tests verify the SSH key merging logic works correctly
+
+it('validates SSH key array merging logic with Coolify key', function () {
+    $coolifyKeyId = 123;
+    $selectedHetznerKeys = [];
+
+    $sshKeys = array_merge(
+        [$coolifyKeyId],
+        $selectedHetznerKeys
+    );
+    $sshKeys = array_unique($sshKeys);
+    $sshKeys = array_values($sshKeys);
+
+    expect($sshKeys)->toBe([123])
+        ->and(count($sshKeys))->toBe(1);
+});
+
+it('validates SSH key array merging with additional Hetzner keys', function () {
+    $coolifyKeyId = 123;
+    $selectedHetznerKeys = [456, 789];
+
+    $sshKeys = array_merge(
+        [$coolifyKeyId],
+        $selectedHetznerKeys
+    );
+    $sshKeys = array_unique($sshKeys);
+    $sshKeys = array_values($sshKeys);
+
+    expect($sshKeys)->toBe([123, 456, 789])
+        ->and(count($sshKeys))->toBe(3);
+});
+
+it('validates deduplication when Coolify key is also in selected keys', function () {
+    $coolifyKeyId = 123;
+    $selectedHetznerKeys = [123, 456, 789];
+
+    $sshKeys = array_merge(
+        [$coolifyKeyId],
+        $selectedHetznerKeys
+    );
+    $sshKeys = array_unique($sshKeys);
+    $sshKeys = array_values($sshKeys);
+
+    expect($sshKeys)->toBe([123, 456, 789])
+        ->and(count($sshKeys))->toBe(3);
+});