chore(deps): widen multi-major constraints

[mpge]

Summary

• Widens five composer.json constraints to additive multi-major ranges, so Symfony 6.4 / 7.x / 8.x and Doctrine ORM 2 / 3 hosts all install cleanly.
• Supersedes the four open Dependabot PRs that would have replaced (rather than extended) the existing constraints, narrowing the support matrix the README advertises.
• Also fixes a pre-existing inconsistency where symfony/mime was already pinned to ^8.0 only.

Changes

Package	Before	After
doctrine/doctrine-bundle	^2.11	^2.11|^3.2
symfony/mime	^8.0	^6.4|^7.0|^8.0
symfony/security-bundle	^6.4|^7.0	^6.4|^7.0|^8.0.8
symfony/uid	^6.4|^7.0	^6.4|^7.0|^8.0.9
symfony/phpunit-bridge (dev)	^6.4|^7.0	^6.4|^7.0|^8.0.8

PHP floor stays at ^8.2 because the 6.4 / 7 install paths remain valid; Symfony 8 only resolves on PHP 8.4+ hosts.

Closes #48, #49, #50, #51.

Test plan

• CI lint job (PHP-CS-Fixer on PHP 8.4) green
• composer install resolves on the CI runner without conflicts