chore(release): 0.2.2 — keep all Symfony components on 7.4

- Add symfony/flex so extra.symfony.require "7.4.*" is enforced for
  transitive components (dependency-injection had drifted to 8.0.15)
- Group Symfony packages in Renovate and restrict them to ~7.4
- Copy symfony.lock in Docker builds so Flex doesn't re-apply recipes
- Add missing 0.2.1 changelog section and cut 0.2.2

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

composer.json

@@ -8,6 +8,7 @@
         "monolog/monolog": "^3.10",
         "symfony/cache": "7.4.*",
         "symfony/console": "7.4.*",
+        "symfony/flex": "^2",
         "symfony/framework-bundle": "7.4.*",
         "symfony/http-client": "7.4.*",
         "symfony/monolog-bundle": "^4.0",
@@ -33,6 +34,7 @@
         "optimize-autoloader": true,
         "sort-packages": true,
         "allow-plugins": {
+            "symfony/flex": true,
             "symfony/runtime": true
         }
     },