Show git commit hash as build number in sidebar footer

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

config/app.php

@@ -15,6 +15,8 @@ return [
 
     'name' => env('APP_NAME', 'Laravel'),
 
+    'git_commit' => env('GIT_COMMIT', 'dev'),
+
     /*
     |--------------------------------------------------------------------------
     | Application Environment