Enable API by default in development mode

- API is now enabled by default when running in development mode
- Production instances keep API disabled by default (existing behavior)
- Uses isDev() helper to determine environment

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

database/seeders/InstanceSettingsSeeder.php

@@ -16,6 +16,7 @@ public function run(): void
         InstanceSettings::create([
             'id' => 0,
             'is_registration_enabled' => true,
+            'is_api_enabled' => isDev(),
             'smtp_enabled' => true,
             'smtp_host' => 'coolify-mail',
             'smtp_port' => 1025,