Remove Symfony-specific build target and composer.phar (#576)

* Remove composer.phar from repository

The 3MB composer.phar binary should not be tracked in git.
It was already listed in .gitignore but had been committed previously.
The sfbuild Makefile target now uses `symfony composer` directly,
consistent with how the build target uses `composer`.

https://claude.ai/code/session_01Y23jrgXnJ6Av6Gf6LdwhMx

* Remove unused sfbuild Makefile target

The sfbuild target was a duplicate of build wrapped with the Symfony CLI.
It was not referenced anywhere (CI, docs, Dockerfile) and was the only
reason composer.phar was committed in the repo.

https://claude.ai/code/session_01Y23jrgXnJ6Av6Gf6LdwhMx

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: fain182

Makefile

@@ -44,12 +44,6 @@ build: ## it launches all the build
 	bin/psalm.phar --no-cache
 	bin/phpunit
 
-sfbuild: ## it launches all the build
-	symfony php composer.phar install
-	PHP_CS_FIXER_IGNORE_ENV=1 symfony php bin/php-cs-fixer fix -v
-	symfony php bin/psalm
-	symfony php bin/phpunit
-
 dt: ##it launches tests using container
 	docker run --rm -it --entrypoint= -v $(PWD):/arkitect phparkitect make test