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

tests/Unit/HetznerSshKeysTest.php

@@ -0,0 +1,53 @@
+<?php
+
+it('merges Coolify key with selected Hetzner keys', function () {
+    $coolifyKeyId = 123;
+    $selectedHetznerKeys = [456, 789];
+
+    // Simulate the merge logic from createHetznerServer
+    $sshKeys = array_merge(
+        [$coolifyKeyId],
+        $selectedHetznerKeys
+    );
+
+    expect($sshKeys)->toBe([123, 456, 789])
+        ->and(count($sshKeys))->toBe(3);
+});
+
+it('removes duplicate SSH key IDs', function () {
+    $coolifyKeyId = 123;
+    $selectedHetznerKeys = [123, 456, 789]; // User also selected Coolify key
+
+    // Simulate the merge and deduplication logic
+    $sshKeys = array_merge(
+        [$coolifyKeyId],
+        $selectedHetznerKeys
+    );
+    $sshKeys = array_unique($sshKeys);
+    $sshKeys = array_values($sshKeys);
+
+    expect($sshKeys)->toBe([123, 456, 789])
+        ->and(count($sshKeys))->toBe(3);
+});
+
+it('works with no selected Hetzner keys', function () {
+    $coolifyKeyId = 123;
+    $selectedHetznerKeys = [];
+
+    // Simulate the merge logic
+    $sshKeys = array_merge(
+        [$coolifyKeyId],
+        $selectedHetznerKeys
+    );
+
+    expect($sshKeys)->toBe([123])
+        ->and(count($sshKeys))->toBe(1);
+});
+
+it('validates SSH key IDs are integers', function () {
+    $selectedHetznerKeys = [456, 789, 1011];
+
+    foreach ($selectedHetznerKeys as $keyId) {
+        expect($keyId)->toBeInt();
+    }
+});