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

.github/workflows/ci.yml

@@ -0,0 +1,186 @@
+name: CI
+
+on:
+  push:
+    branches: [main, develop]
+  pull_request:
+    branches: [main, develop]
+
+jobs:
+  # =============================================================================
+  # Backend Tests - PHP 8.5, PHPStan, PHPUnit
+  # =============================================================================
+  test-backend:
+    name: Backend Tests
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: backend
+
+    services:
+      postgres:
+        image: postgres:18.1-alpine
+        env:
+          POSTGRES_DB: classeo_test
+          POSTGRES_USER: classeo
+          POSTGRES_PASSWORD: classeo
+        ports:
+          - 5432:5432
+        options: >-
+          --health-cmd pg_isready
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
+
+      redis:
+        image: redis:7.4-alpine
+        ports:
+          - 6379:6379
+        options: >-
+          --health-cmd "redis-cli ping"
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.5'
+          extensions: intl, pdo_pgsql, amqp, redis, zip
+          coverage: xdebug
+
+      - name: Get Composer cache directory
+        id: composer-cache
+        run: echo "dir=$(composer config cache-files-dir)" >> $GITHUB_OUTPUT
+
+      - name: Cache Composer dependencies
+        uses: actions/cache@v4
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: ${{ runner.os }}-composer-
+
+      - name: Install dependencies
+        run: composer install --prefer-dist --no-progress
+
+      - name: Run PHP CS Fixer (check)
+        run: composer cs-check
+
+      - name: Run PHPStan
+        run: composer phpstan
+
+      - name: Run PHPUnit
+        run: composer test
+        env:
+          DATABASE_URL: postgresql://classeo:classeo@localhost:5432/classeo_test?serverVersion=18
+          REDIS_URL: redis://localhost:6379
+
+      - name: Run BC Isolation Check
+        working-directory: .
+        run: ./scripts/check-bc-isolation.sh
+
+  # =============================================================================
+  # Frontend Tests - Vitest, Playwright
+  # =============================================================================
+  test-frontend:
+    name: Frontend Tests
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: frontend
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+
+      - name: Setup pnpm
+        uses: pnpm/action-setup@v3
+        with:
+          version: 9
+
+      - name: Get pnpm store directory
+        id: pnpm-cache
+        run: echo "STORE_PATH=$(pnpm store path)" >> $GITHUB_OUTPUT
+
+      - name: Cache pnpm dependencies
+        uses: actions/cache@v4
+        with:
+          path: ${{ steps.pnpm-cache.outputs.STORE_PATH }}
+          key: ${{ runner.os }}-pnpm-store-${{ hashFiles('**/pnpm-lock.yaml') }}
+          restore-keys: ${{ runner.os }}-pnpm-store-
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Run linter
+        run: pnpm run lint
+
+      - name: Run TypeScript check
+        run: pnpm run check
+
+      - name: Run unit tests
+        run: pnpm run test
+
+      - name: Install Playwright browsers
+        run: pnpm exec playwright install --with-deps
+
+      - name: Run E2E tests
+        run: pnpm run test:e2e
+
+      - name: Upload Playwright report
+        uses: actions/upload-artifact@v4
+        if: failure()
+        with:
+          name: playwright-report
+          path: frontend/playwright-report/
+          retention-days: 7
+
+  # =============================================================================
+  # Naming Conventions Check
+  # =============================================================================
+  check-naming:
+    name: Naming Conventions
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Run Naming Check
+        run: ./scripts/check-naming.sh
+
+  # =============================================================================
+  # Build Check
+  # =============================================================================
+  build:
+    name: Build Check
+    runs-on: ubuntu-latest
+    needs: [test-backend, test-frontend]
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Build backend image
+        uses: docker/build-push-action@v6
+        with:
+          context: ./backend
+          push: false
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+
+      - name: Build frontend image
+        uses: docker/build-push-action@v6
+        with:
+          context: ./frontend
+          push: false
+          cache-from: type=gha
+          cache-to: type=gha,mode=max