Add auth0-tenant-health CodeBundle

[rw-codebundle-agent]

Closes #181 (design-spec: auth0-tenant-health)

Implements the auth0-tenant-health CodeBundle in the rw-cli-codecollection.

What it monitors

Monitors the overall health of an upstream Auth0 tenant:

• Tenant Service Availability: DNS resolution + well-known discovery + Management API reachability (5xx/unreachable detection).
• Custom Domain Health: DNS, TLS cert expiry, and verification status for each custom domain.
• Tenant Error Logs: Buckets Logs API events by type, flags repeated error/warn/anomaly classes.
• Login Failures & Anomalous Activity: Detects elevated login failures, blocked users, brute-force patterns.
• Rate Limit & Throttling: Management API rate-limit utilization + limit/429 log signals.
• Log Stream Delivery Health: Verifies log streams are active and delivering.

Includes an in-repo sli.robot producing a 0-1 health score across six binary dimensions, alongside runbook, slx/taskset/sli templates, generation rules, and static test scaffolding.

Deviation from design spec

• Secret consumed as a single AUTH0_MGMT_CREDENTIALS value (JSON with client_id/client_secret, or a raw MAPI token) rather than separate CLIENT_ID/CLIENT_SECRET variables, to keep the curl+jq scripts self-contained and match the collection's existing REST-based credential pattern.
• Generation rules use a custom static auth0_tenant resourceType scoped by a single tenant qualifier (Auth0 is not a natively-discovered RunWhen platform); the operator supplies AUTH0_TENANT.

Validation

python -m scorer.score codebundles/auth0-tenant-health passes 104/104 (threshold 70). .test/validate-all-tests.sh static checks pass.