feat: enable IPv6 support for IPv6-only Kubernetes environments

[olexii4]

What does this PR do?

This PR adds IPv6 support in Eclipse Che Dashboard to enable operation in IPv6-only network environments. As Kubernetes platforms (particularly OpenShift Container Platform 4.20) migrate to IPv6, the dashboard must handle IPv6 addresses correctly in URLs, API calls, and server bindings.

The implementation involved minimal, focused changes to URL validation patterns and server configuration, enabling full IPv6 support while maintaining complete backward compatibility with IPv4-only and dual-stack environments.

---

Background

The Eclipse Che Dashboard previously failed to operate in IPv6-only environments due to:

1. Server Binding Limitation: Backend server bound only to 0.0.0.0 (IPv4-only)
2. URL Validation Issues: Regular expressions rejected IPv6 bracket notation (e.g., http://[::1]:8080)
3. Git Repository Access: Factory flows could not handle IPv6 git server URLs
4. Container Registry Configuration: Users could not configure IPv6 container registries

Impact

• Critical: Dashboard completely non-functional in IPv6-only Kubernetes clusters
• Blocking: OpenShift Container Platform 4.20 migration to IPv6
• User Experience: Inability to create workspaces from IPv6-hosted git repositories

IPv6 Bracket Notation

IPv6 addresses in URLs require square brackets to distinguish the address from port numbers:

• ✅ Correct: http://[2001:db8::1]:8080/repo.git
• ❌ Incorrect: http://2001:db8::1:8080/repo.git (ambiguous - is 8080 part of address or port?)

---

Screenshot/screencast of this PR

What issues does this PR fix or reference?

fixes eclipse-che/che#23674

Is it tested? How?

Tested manually on an IPv6-only OpenShift cluster (OCP 4.20.x) using the deployment + validation scripts in the testing repository:

https://github.com/olexii4/deploy-che-ipv6-chectl.git

How to reproduce the test:

1. Provision an IPv6-only OpenShift cluster (e.g. via OpenShift CI cluster-bot).
2. Predownload required images to local cache (this step can be done before cluster access):

   ./scripts/mirror-images-to-registry.sh \
     --mode full \
     --prefetch-only \
     --cache-dir ~/.cache/che-ipv6-mirror

3. Mirror cached images to the cluster's local registry:

   ./scripts/mirror-images-to-registry.sh \
     --kubeconfig <cluster-bot-kubeconfig> \
     --mode full \
     --cache-dir ~/.cache/che-ipv6-mirror \
     --dashboard pr-1442

4. Deploy Eclipse Che manually from OLM bundles:

   ./scripts/deploy-che-manual-from-bundles.sh \
     --kubeconfig <cluster-bot-kubeconfig>

5. Deploy IPv6 test infrastructure (in-cluster git/devfile servers) and verify the services respond over IPv6:

   ./scripts/test-ipv6-validation.sh \
     --kubeconfig <cluster-bot-kubeconfig> \
     --repo-url git@github.com:che-samples/web-nodejs-sample.git \
     --devfile-url https://registry.devfile.io/devfiles/nodejs-angular/2.2.1

6. Open the printed factory URLs in the Che dashboard (via HTTP proxy from kubeconfig) and confirm:
   • IPv6 bracket-notation URLs are accepted by the UI validation
   • Workspace creation succeeds when using the in-cluster IPv6 git/devfile URLs

Notes:

• On IPv6-only clusters, image mirroring is required. The mirror script applies ImageTagMirrorSet/ImageDigestMirrorSet (+ ICSP for compatibility).
• The deployment script automatically creates required resources: webhook TLS certificates, leader election RBAC, and DevWorkspace CRDs.
• The mirroring workflow is documented in scripts/mirror-images-to-registry.md.
• Each skopeo copy is guarded by a per-image timeout (SKOPEO_TIMEOUT_SECONDS, default 900s) to avoid hangs.
• The cluster is accessible only via HTTP proxy (provided in kubeconfig's proxy-url field).

All required commands and expected outputs are documented in the repository README.md.

Release Notes

Docs PR

[che-bot]

Click here to review and test in web IDE:

[github-actions]

Docker image build succeeded: quay.io/eclipse/che-dashboard:pr-1442

kubectl patch command

kubectl patch -n eclipse-che "checluster/eclipse-che" --type=json -p="[{"op": "replace", "path": "/spec/components/dashboard/deployment", "value": {containers: [{image: "quay.io/eclipse/che-dashboard:pr-1442", name: che-dashboard}]}}]"

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.80%. Comparing base (c2b7c3e) to head (546b326).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1442      +/-   ##
==========================================
+ Coverage   92.78%   92.80%   +0.01%     
==========================================
  Files         522      522              
  Lines       49321    49320       -1     
  Branches     3690     3694       +4     
==========================================
+ Hits        45764    45771       +7     
+ Misses       3518     3510       -8     
  Partials       39       39              

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[github-actions]

Docker image build succeeded: quay.io/eclipse/che-dashboard:pr-1442

kubectl patch command

kubectl patch -n eclipse-che "checluster/eclipse-che" --type=json -p="[{"op": "replace", "path": "/spec/components/dashboard/deployment", "value": {containers: [{image: "quay.io/eclipse/che-dashboard:pr-1442", name: che-dashboard}]}}]"

[svor]

/retest

[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: olexii4, tolusha

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[openshift-ci]

New changes are detected. LGTM label has been removed.

[github-actions]

Docker image build succeeded: quay.io/eclipse/che-dashboard:pr-1442

kubectl patch command

kubectl patch -n eclipse-che "checluster/eclipse-che" --type=json -p="[{"op": "replace", "path": "/spec/components/dashboard/deployment", "value": {containers: [{image: "quay.io/eclipse/che-dashboard:pr-1442", name: che-dashboard}]}}]"