[tests-only][full-ci][k8s] test(ci): run e2e test against k8s deployment

[ishabaral]

Description

This PR adds a new e2e-tests job to .github/workflows/k8s.yml that runs Playwright UI tests against the k3d/Helm-deployed oCIS cluster.

To do this, tests/acceptance/run-e2e.py now supports a K8S=true mode: when set, it skips building/starting a local oCIS binary entirely and just points Playwright at the already-running k8s deployment (TEST_SERVER_URL). This is the same script acceptance-tests.yml already uses for local-binary e2e runs — it now has two modes instead of a separate copy-pasted flow.

Scope of this PR:
Just to ensure the e2e works, this PR only runs the smoke suite. The remaining suites will be added in follow-up PRs.

Related Issue

• Part of : [QA] Run e2e tests on Kubernetes deployment #13007

Motivation and Context

How Has This Been Tested?

• test environment: GitHub Actions, PR title containing k8s to trigger the workflow
• test case 1: e2e-smoke-k8s job spins up the k3d cluster, deploys oCIS via Helm, and runs the smoke Playwright suite against it , all specs pass
• test case 2: existing api-tests job is unaffected (unchanged steps, still green)
• ...

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Technical debt
• Tests only (no source changes)

Checklist:

• Code changes
• Unit tests added
• Acceptance tests added
• Documentation ticket raised:

[kw-security]

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