fix(BA-3800): Endpoint status does not consider DEGRADED routes when determining DEGRADED status

[jopemachine]

resolves #7869 (BA-3800)

Checklist: (if applicable)

• Milestone metadata specifying the target backport version
• Mention to the original issue
• Installer updates including:
  • Fixtures for db schema changes
  • New mandatory config options
• Update of end-to-end CLI integration tests in ai.backend.test
• API server-client counterparts (e.g., manager API -> client SDK)
• Test case(s) to:
  • Demonstrate the difference of before/after
  • Demonstrate the flow of abstract/conceptual models with a concrete implementation
• Documentation
  • Contents in the docs directory
  • docstrings in public interfaces and type annotations

[HyeockJinKim]

I think unreachable_service_count sounds better than problematic_service_count.

[jopemachine]

I think TERMINATED, FAILED_TO_START route is also "unreachable", so it seems ambiguous to name this variable 🤔

[Copilot]

Pull request overview

This PR fixes a bug where endpoint status resolution did not consider routes with DEGRADED status when determining if an endpoint should have DEGRADED status. Previously, only UNHEALTHY routes were checked, causing endpoints with DEGRADED routes to incorrectly show PROVISIONING status instead of DEGRADED.

Key changes:

• Updated endpoint status resolution logic to check for both UNHEALTHY and DEGRADED routes
• Renamed unhealthy_service_count to problematic_service_count for better clarity
• Added test coverage for the scenario with mixed healthy and degraded routes

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/ai/backend/manager/api/gql_legacy/endpoint.py	Updated resolve_status method to include DEGRADED routes in the check for problematic routes, and renamed the counter variable for clarity
tests/unit/manager/api/endpoint/test_types.py	Added test case to verify that endpoints with both healthy and degraded routes correctly return DEGRADED status
changes/7870.fix.md	Added changelog entry for the fix

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[Copilot]

The changelog filename is 7870.fix.md but the PR description mentions resolving issue #7869. The filename should match the issue number being resolved. Please rename this file to 7869.fix.md to maintain consistency.