test: keep smart routing reset fixture within one hour - #77

Root cause

The Ubuntu test job in #76 failed in TestSmartRouting at routing_test.go:119: it got s#b s#c s#a rather than s#c s#b s#a in the "week, then five hours" case (failed job). The test uses time.Now() to create weekly resets for b and c one minute apart. Routing compares their reset times after truncating them to an hour. If the test starts in the final minute of an hour, b and c land in different hour buckets, so b correctly goes before c and the test's expected five-hour tie-breaker does not apply.

This fixture predates #76 and is unrelated to its disabled-key change. The provider tests passed in that run.

Fix

Anchor only this routing fixture at 20 minutes into the current hour. Both weekly resets are then in the same hour, so the test consistently checks the five-hour tie-breaker it names. The other timing and rest assertions keep their real-time anchor.

Tests

• Reproduced the original failure on current main by forcing the test's now to time.Now().Truncate(time.Hour).Add(59*time.Minute + 30*time.Second): the exact s#b s#c s#a failure.
• With this fix, TZ=UTC go test ./internal/gateway -run '^TestSmartRouting$' -count=1 passed; TZ=UTC go test ./internal/gateway ./internal/provider -count=1 passed.
• Forcing only routingNow to the synthetic 59:30 boundary after the fix reproduces the same failure. Restoring the 20-minute anchor returns the test to green.
• Full go test ./... could not compile the GUI in my Linux container: GTK4/WebKitGTK 6 development libraries are absent. The CI workflow installs GTK3/WebKitGTK 4.1 and uses -tags gtk3; the relevant gateway/provider tests above ran locally without GUI dependencies.