Stop tracking .env files and sanitize docker/.env.dist

.env, .env.dev, .env.prod, .env.test, and docker/.env contained real
production secrets and were tracked in git despite the Symfony
convention of keeping them local-only. Untrack them and ignore them
going forward; docker/.env.dist stays as a template but now uses
placeholder values instead of live credentials.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.gitignore

@@ -1,5 +1,9 @@
 
 ###> symfony/framework-bundle ###
+/.env
+/.env.dev
+/.env.prod
+/.env.test
 /.env.local
 /.env.local.php
 /.env.*.local
@@ -30,3 +34,7 @@ yarn-error.log
 ###< symfony/webpack-encore-bundle ###
 
 /.idea
+
+###> docker env ###
+/docker/.env
+###< docker env ###