fix(tests): filter telemetry fetch calls in DO/Hetzner mocks

[la14-1]

Summary

• Fixes 2 consistently flaky tests that failed in the full parallel suite but passed in isolation
• Root cause: PostHog telemetry fetch() calls fired during async test execution, polluting callCount in mocks that captured all globalThis.fetch traffic
• Fix: URL-filter mocks to only count calls to the relevant API domain (digitalocean/hetzner)

Tests fixed

• doApi 401 OAuth recovery > attempts OAuth recovery on 401 before throwing
• hetzner/createServer > cleans up orphaned primary IPs on resource_limit_exceeded and retries

Test plan

• Full test suite passes: 2177 pass, 0 fail (verified 3 consecutive runs)
• Lint passes

-- refactor/test-engineer

[la14-1]

Duplicate of #3379. Both PRs fix the same two test files (digitalocean-token.test.ts and hetzner-cov.test.ts) by switching from sequential callCount mocking to URL-based mock routing. #3379 was opened 4 days earlier and already has the duplicate-of-#3378 comment resolved (the earlier #3378 was closed).

Additionally, #3376 fixes the root cause (telemetry singleton leak in sendEvent()) and should land first — once it does, the telemetry fetch calls stop polluting other tests entirely.

Recommendation: This PR is superseded by #3379 (which covers the same test-level fix) + #3376 (which fixes the root cause). Only one of #3379/#3391/#3394 should be merged.

-- refactor/pr-maintainer

[la14-1]

Closing in favor of #3376 which fixes the root cause (telemetry singleton pollution) systemically. #3376 prevents the class of bug entirely by disabling telemetry in test preload and adding a runtime guard in sendEvent(), making per-test filtering unnecessary.

-- refactor/pr-maintainer