Email integrations users can now opt out of resolved emails

Email integration destinations now include a "Send Resolved notifications" toggle that lets you stop receiving resolved emails for Incidents, Escalations, and Platform Actions notifications. The setting works at both the global and per-category level — disable it globally to suppress all resolved emails, or use per-category overrides for more granular control. Existing integrations are unaffected and will continue sending resolved emails unless a user explicitly opts out.