Implement TTFB monitoring via probes

[henzigo]

Adds production-only TTFB monitoring by generating Prometheus Operator Probe resources (via blackbox-exporter)

[Copilot]

Pull request overview

Adds production-only TTFB monitoring by generating Prometheus Operator Probe resources (via blackbox-exporter) and introduces test scenarios validating domain selection, path normalization, and HTTP basic-auth embedding.

Changes:

• Add deploy/parts/probes.sh to generate TTFB Probe manifests and include them in webserver kustomization.
• Add a Probe manifest template under kubernetes/manifest-templates/.
• Add three test scenarios (ttfb-default-domain, ttfb-custom-domain, ttfb-http-auth) with expected rendered manifests and scenario wiring; document usage in README.md and upgrade steps in UPGRADE.md.

Reviewed changes

Copilot reviewed 38 out of 38 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
deploy/parts/probes.sh	Generates Probe YAMLs from TTFB_PROBES, optionally embeds HTTP auth, and amends kustomization resources.
kubernetes/manifest-templates/probe.template.yaml	Template for Prometheus Operator Probe objects used by the generator.
tests/lib/scenario-base.sh	Ensures probe generation runs as part of scenario manifest generation.
tests/scenarios/**	Adds scenarios and golden expected outputs covering default/custom/auth-protected probe targets.
README.md	Documents how to enable/configure TTFB probes.
UPGRADE.md	Notes upgrade steps for enabling probes in downstream projects.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.