feat(ci): add go vet and gofmt check to backend CI

INF-04: Backend CI now runs go vet and gofmt to catch issues early.

.github/workflows/backend-ci.yml

@@ -30,6 +30,12 @@ jobs:
       - name: Download deps
         run: go mod download
 
+      - name: Go vet and format check
+        run: |
+          go vet ./...
+          test -z "$(gofmt -l .)"
+        working-directory: veza-backend-api
+
       - name: Run govulncheck
         run: |
           go install golang.org/x/vuln/cmd/govulncheck@latest