chore(deps): bump Symfony to 7.4 and add GraphQL client bundles

- symfony/* pinned to 7.4.* (was 7.1.*)
- eightpoints/guzzle-bundle ^8.6 and idci/graphql-client-bundle ^2.0 added
- phpunit/phpunit ^11.5 and symfony/phpunit-bridge ^7.4 added as dev deps
- Bundles registered in config/bundles.php
- Guzzle and GraphQL client configured via YAML package configs

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

config/packages/eight_points_guzzle.yaml

@@ -0,0 +1,7 @@
+eight_points_guzzle:
+    clients:
+        github_graphql:
+            base_url: 'https://api.github.com/graphql'
+            options:
+                headers:
+                    Authorization: 'Bearer %env(GITHUB_TOKEN)%'