Skip cancelled events in city redirect and latest-site hints

[dd32]

Summary

• Modifies get_latest_site() in sunrise-wordcamp.php to exclude sites whose WordCamp tracker post has wcpt-cancelled status
• Updates all three query paths in get_latest_home_url() in latest-site-hints.php with the same exclusion
• Cancelled event sites remain accessible at their direct URLs (e.g., city.wordcamp.org/2025/) - only the automatic redirect is affected

Closes #1600

Test plan

• Verify that city.wordcamp.org redirects to the most recent non-cancelled event
• Verify that the "See the next edition" banner on older events does not link to a cancelled event
• Verify that a cancelled event site is still directly accessible at its full URL
• Verify the redirect still works correctly for cities with no cancelled events

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