chore(ci): make tag step idempotent

Author: agneszitte

.github/workflows/ci.yml

@@ -189,5 +189,10 @@ jobs:
         run: |
           git config user.email "info@platform.uno"
           git config user.name "Uno DevOps"
-          git tag $env:NBGV_SemVer2
-          git push origin $env:NBGV_SemVer2
+          git rev-parse --verify "refs/tags/$env:NBGV_SemVer2" 2>$null
+          if ($LASTEXITCODE -eq 0) {
+            Write-Host "Tag $env:NBGV_SemVer2 already exists, skipping."
+          } else {
+            git tag $env:NBGV_SemVer2
+            git push origin $env:NBGV_SemVer2
+          }