feat: add health status route in backend for users

[amandazhuyilan]

Pull Request

Summary

SBP-406: Surfaces a coarse health signal to SBP-bundle users on the job details page, so they know when job status/logs may be stale or submissions slow.

Changes

• New route GET /api/health/components, gated to SBP-bundle approved users (same gate as workflow submission)
• Returns a single overallStatus + generic message — does not identify which component is affected message is null when healthy, otherwise a generic "services unavailable, data may be stale" notice
• Reuses the existing health service (probes seqera_api, seqera_compute_env, seqera_tower_agent); overallStatus = worst of the three
• Added stale-while-revalidate caching: expired-cache reads return the last result instantly and refresh in the background, so users never block on the ~2s probes (only a cold start blocks)
• Force-refresh is admin-only (/admin/api/system-status); the user-facing endpoint always serves from cache
• Added ComponentsHealthResponse schema + to_components_health_dict() projection

Status meanings

• healthy — all components reachable & operational (Seqera API 2xx, compute env AVAILABLE); no message shown
• degraded — slow/provisioning but not failed (e.g. compute env CREATING, or unknown state); warning shown
• unhealthy — a component is down/failing (Seqera API non-2xx/timeout/bad token, or compute env ERRORED/OFFLINE/INVALID); warning shown

How to Test

All CI tests shall pass!

Type of change

• 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)
• Documentation update

Checklist

• I have added tests that prove my fix is effective or that my feature works
• I have added or updated documentation where necessary
• I have run linting and unit tests locally
• The code follows the project's style guidelines

[marius-mather]

looks good but I'm not sure if we want to allow the force-refresh on the user-facing API, seems safer to keep that admin only unless there's a definite need for it

[vtnphan]

Good to go!