chore: add workflow to delete Docker tags

.github/workflows/delete-docker-tag.yml

@@ -0,0 +1,26 @@
+name: Delete Docker tag
+
+on:
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: 'Tag to delete (e.g. 2.10.0)'
+        required: true
+
+jobs:
+  delete-tag:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Delete tag from Docker Hub
+        run: |
+          TOKEN=$(curl -s -X POST \
+            -H "Content-Type: application/json" \
+            -d '{"username":"${{ secrets.DOCKERHUB_USERNAME }}","password":"${{ secrets.DOCKERHUB_TOKEN }}"}' \
+            https://hub.docker.com/v2/users/login | jq -r .token)
+
+          STATUS=$(curl -s -o /dev/null -w "%{http_code}" -X DELETE \
+            -H "Authorization: JWT ${TOKEN}" \
+            "https://hub.docker.com/v2/repositories/mauriceboe/trek/tags/${{ inputs.tag }}/")
+
+          echo "Response: $STATUS"
+          [ "$STATUS" = "204" ] && echo "Tag deleted." || echo "Failed (HTTP $STATUS)."