feat: Setup projet Classeo avec infrastructure Docker et architecture DDD

Configure l'environnement de développement complet avec Docker Compose,
structure DDD 4 Bounded Contexts, et pipeline CI/CD GitHub Actions.

Corrections compatibilité CI:
- Symfony 8 nécessite monolog-bundle ^4.0 (la v3.x ne supporte que jusqu'à Symfony 7)
- ESLint v9 nécessite flat config (eslint.config.js) - le format .eslintrc.cjs est obsolète

backend/config/packages/doctrine.yaml

@@ -0,0 +1,52 @@
+doctrine:
+    dbal:
+        url: '%env(resolve:DATABASE_URL)%'
+        profiling_collect_backtrace: '%kernel.debug%'
+
+    orm:
+        validate_xml_mapping: true
+        naming_strategy: doctrine.orm.naming_strategy.underscore_number_aware
+        auto_mapping: true
+        mappings:
+            # Infrastructure mappings - keep entities separate from Domain
+            Administration:
+                type: attribute
+                is_bundle: false
+                dir: '%kernel.project_dir%/src/Administration/Infrastructure/Persistence/Mapping'
+                prefix: 'App\Administration\Infrastructure\Persistence\Mapping'
+                alias: Administration
+            Scolarite:
+                type: attribute
+                is_bundle: false
+                dir: '%kernel.project_dir%/src/Scolarite/Infrastructure/Persistence/Mapping'
+                prefix: 'App\Scolarite\Infrastructure\Persistence\Mapping'
+                alias: Scolarite
+            VieScolaire:
+                type: attribute
+                is_bundle: false
+                dir: '%kernel.project_dir%/src/VieScolaire/Infrastructure/Persistence/Mapping'
+                prefix: 'App\VieScolaire\Infrastructure\Persistence\Mapping'
+                alias: VieScolaire
+            Communication:
+                type: attribute
+                is_bundle: false
+                dir: '%kernel.project_dir%/src/Communication/Infrastructure/Persistence/Mapping'
+                prefix: 'App\Communication\Infrastructure\Persistence\Mapping'
+                alias: Communication
+        controller_resolver:
+            auto_mapping: false
+
+when@test:
+    doctrine:
+        dbal:
+            dbname_suffix: '_test%env(default::TEST_TOKEN)%'
+
+when@prod:
+    doctrine:
+        orm:
+            query_cache_driver:
+                type: pool
+                pool: doctrine.system_cache_pool
+            result_cache_driver:
+                type: pool
+                pool: doctrine.result_cache_pool