feat(ci): improve Docker image cleanup workflow

Replace old cleanup workflow with improved implementation:
- Migrate from snok/container-retention-policy to dataaxiom/ghcr-cleanup-action
- Automatic package discovery (no hardcoded package names needed)
- More flexible retention policies (keep 2 most recent tagged images)
- Better handling of partial and untagged images
- Remove Discord notifications to reduce dependencies
- Maintain monthly cleanup schedule (15th at midnight UTC)
- Add manual workflow_dispatch trigger for on-demand cleanup

Author: SimplicityGuy

.github/workflows/cleanup-images.yml

@@ -0,0 +1,28 @@
+---
+name: Cleanup Docker Images
+
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: "0 0 15 * *"  # Monthly on the 15th at midnight UTC
+
+concurrency:
+  group: cleanup-images
+  cancel-in-progress: false
+
+jobs:
+  cleanup:
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    permissions:
+      packages: write  # Required to delete packages
+      contents: read
+    steps:
+      - name: 🧹 Cleanup Docker Images
+        uses: dataaxiom/ghcr-cleanup-action@cd0cdb900b5dbf3a6f2cc869f0dbb0b8211f50c4  # v1.0.16
+        with:
+          delete-partial-images: true
+          delete-untagged: true
+          keep-n-tagged: 2
+          older-than: 30 days
+          token: ${{ secrets.GITHUB_TOKEN }}