fix(env): validate Docker-compatible variable keys

Add shared environment variable key validation and normalization for Livewire forms and models, allowing Docker-compatible keys while rejecting invalid entries such as keys containing equals signs. Also quote Railpack build environment and secret arguments safely.

tests/Feature/EnvironmentVariableKeyValidationTest.php

@@ -0,0 +1,39 @@
+<?php
+
+use App\Livewire\Project\Shared\EnvironmentVariable\Add;
+use Livewire\Livewire;
+
+it('rejects environment variable keys Docker cannot represent in the add form', function () {
+    Livewire::test(Add::class)
+        ->set('key', 'BAD=KEY')
+        ->set('value', 'value')
+        ->call('submit')
+        ->assertHasErrors(['key' => 'regex']);
+});
+
+it('allows Docker-compatible environment variable keys in the add form', function (string $key) {
+    Livewire::test(Add::class)
+        ->set('key', $key)
+        ->set('value', 'value')
+        ->call('submit')
+        ->assertHasNoErrors()
+        ->assertDispatched('saveKey', function ($event, array $data) use ($key) {
+            return data_get($data, 'key') === $key || data_get($data, '0.key') === $key;
+        });
+})->with([
+    'starts with digit' => '1BAD',
+    'hyphen' => 'BAD-KEY',
+    'dot' => 'node.name',
+    'uppercase dots' => 'XPACK.SECURITY.ENABLED',
+]);
+
+it('trims surrounding whitespace in environment variable keys in the add form', function () {
+    Livewire::test(Add::class)
+        ->set('key', ' node.name ')
+        ->set('value', 'value')
+        ->call('submit')
+        ->assertHasNoErrors()
+        ->assertDispatched('saveKey', function ($event, array $data) {
+            return data_get($data, 'key') === 'node.name' || data_get($data, '0.key') === 'node.name';
+        });
+});