refactor(ci): migrate PHP setup to Docker for testing workflow

.gitea/workflows/test.yml

@@ -12,29 +12,26 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v4
-        
-      - name: Set up PHP
-        uses: shivammathur/setup-php@v2
-        with:
-          php-version: "8.4"
-          extensions: intl, zip, opcache
-          coverage: none
 
-      - name: Cache Composer dependencies
-        uses: actions/cache@v4
-        with:
-          path: ~/.composer/cache
-          key: composer-${{ hashFiles('composer.lock') }}
-          restore-keys: composer-
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
 
-      - name: Install dependencies
-        run: composer install --no-interaction --prefer-dist
+      - name: Build dev image (PHP 8.4 + composer deps)
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          file: Dockerfile.dev
+          target: dev
+          load: true
+          tags: graph-dev:ci
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
 
       - name: Run PHPUnit
-        run: vendor/bin/phpunit --testdox
+        run: docker run --rm graph-dev:ci vendor/bin/phpunit --testdox
 
       - name: Run PHPStan
-        run: composer phpstan
+        run: docker run --rm graph-dev:ci composer phpstan
 
   docker-build:
     runs-on: ubuntu-latest