Add a live e2e test for the Conjur-JWT-only, Secret-free install path

\`hack/ark/test-e2e.sh\` (run via \`make ark-test-e2e\`) only exercises the legacy username/password auth path: it hard-requires \`ARK_USERNAME\`/\`ARK_SECRET\`/\`ARK_SUBDOMAIN\` and always writes them into a Secret. The \`helm upgrade\` it runs never sets \`config.cyberark.serviceId\`, so Conjur JWT auth has no live e2e coverage at all.

Since #838 added \`config.cyberark.subdomain\`, a Conjur-JWT-only install (\`config.cyberark.serviceId\` set, \`config.cyberark.subdomain\` set, no Secret whatsoever) is possible but has never been exercised against a live cluster.

Add a second e2e path alongside the existing one:
- Sets \`config.cyberark.serviceId\` and \`config.cyberark.subdomain\` via \`--set\`, no Secret created.
- Reuses the same onboarding/authenticator setup the existing script assumes, or documents what's needed.
- Asserts the same "Data sent successfully" log line as the legacy path.

Leave the existing legacy-path script untouched — it's the backward-compatibility path and should keep testing exactly what it tests today.

Start with hack/ark/test-e2e.sh and run it through make ark-test-e2e to understand the existing legacy path and its onboarding/authenticator assumptions. Add a second live path using config.cyberark.serviceId and config.cyberark.subdomain without creating a Secret, and verify the same "Data sent successfully" log line while leaving the legacy path unchanged.

Vom Indexierungsmodell aus dem Issue-Text verfasst.