Prepare v1.2.2 release

[sk9-devops]

Summary

• Bumps release-facing references from v1.2.1 to v1.2.2 across manifests, Kustomize overlays, GitOps examples, docs, issue template, and publish workflow defaults.
• Adds a latest stable install command for the global-scoped manifest while keeping the immutable v1.2.2 pinned command for production change control.
• Updates the docs-site visible version and changelog entry for v1.2.2.

Dependabot / Security Scope

This release prep includes the already-merged, previously approved high-priority dependency/security update from the current main history:

• google.golang.org/grpc and related Go module dependency updates

No new Dependabot changes were added in this release-prep branch.

Validation

• custom-gcl passed with 0 issues
• go test ./... passed
• git diff --check passed
• Verified no current-facing v1.2.1 references remain outside historical changelog entries
• Verified no typo reference to lates remains

Release Note

After this PR merges and main checks pass, create tag v1.2.2 from the validated main commit, publish the GHCR image, and update the remote latest branch to this validated release commit so the latest stable install command resolves.