fix: use setup-go action instead of container image for CI tests

.forgejo/workflows/deploy.yaml

@@ -11,12 +11,16 @@ jobs:
   # Job 1: Run Backend Tests
   test-backend:
     runs-on: docker
-    container:
-      image: golang:1.24-alpine
     steps:
       - name: Checkout code
         uses: https://github.com/actions/checkout@v4
 
+      - name: Setup Go
+        uses: https://github.com/actions/setup-go@v5
+        with:
+          go-version: '1.24'
+          cache-dependency-path: backend/go.sum
+
       - name: Install dependencies
         run: |
           cd backend