Org overviews bias toward high-signal releases

Changed

• Org overviews now bias toward high-importance releases — high-signal releases (importance ≥ 4) are prioritized at every selection stage so a landmark update isn't crowded out by later churn; unscored releases are treated as normal priority rather than penalized.
• Site footer reorganized — a new Collections column links directly to featured collections; Webhooks is now listed under Docs; an uploads.sh cross-link appears in the footer bar.