Scaffold Symfony 8 app with Bootstrap/DataTables and Docker stack

- Symfony 8.1 webapp skeleton on PHP 8.5 (AssetMapper/importmap, no Node)
- Form-login gate: User entity, security.yaml, SecurityController,
  app:user:create command, initial migration (user + messenger_messages)
- Bootstrap 5 + DataTables layout (base/login/home templates); any
  table.datatable is auto-initialised
- trusted_proxies/headers wired for the shared Nginx Proxy Manager
- Docker (servers only): docker-compose.yml (php:8.5-fpm-alpine,
  nginx:1.30-alpine, mariadb:12.3; host ports 8085/3310; external
  docker_default network) + docker/{Dockerfile,php.ini,nginx,setup.sh,restart.sh}
- .env with CHANGEME placeholders (no secrets), .gitattributes enforces
  LF so the deploy scripts stay runnable on Linux

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

.gitattributes

@@ -0,0 +1,20 @@
+# Normalise everything to LF in the repo (and in working trees). Keeps the
+# Docker shell scripts runnable on the Linux servers regardless of the OS a
+# commit was made from. Matches .editorconfig (end_of_line = lf).
+* text=auto eol=lf
+
+*.sh        text eol=lf
+/bin/console text eol=lf
+/bin/phpunit text eol=lf
+
+# Binaries - never touch.
+*.png binary
+*.jpg binary
+*.jpeg binary
+*.gif binary
+*.ico binary
+*.woff binary
+*.woff2 binary
+*.ttf binary
+*.eot binary
+*.pdf binary