Route stack alerts to specific Discord, Slack, or webhook channels instead
of the single global endpoint. Includes per-rule enable/disable, priority
ordering, and automatic fallback to global agents when no rule matches.
- Add notification_routes table, interface, and CRUD in DatabaseService
- Add routing logic in NotificationService.dispatchAlert with optional stackName
- Pass stack context from MonitorService (crash/health) and SchedulerService
- Add 5 API endpoints gated with requireAdmin + requireAdmiral
- Add NotificationRoutingSection UI with Combobox stack picker, channel tabs
- Parallel webhook dispatch via Promise.allSettled
- 10 unit tests covering routing, fallback, and edge cases
- Documentation with screenshots at docs/features/notification-routing.mdx