feat: add incident management system with user reporting

- Status page (status.viktorbarzin.me): incident cards with SEV badges,
  expandable timelines, postmortem links, user report rendering
- Issue templates on infra repo for user outage reports
- CronJob reads incidents + user-reports from ViktorBarzin/infra
- "Report an Outage" button on status page links to infra repo
- Post-mortem agents restored (4-stage pipeline: triage → investigation
  → historian → report writer) with updated paths and issue linking
- Post-mortem skill/template updated to link reports to GitHub Issues
  and manage postmortem-required/postmortem-done labels
- Labels: incident, sev1-3, user-report, postmortem-required,
  postmortem-done on infra repo

[ci skip]

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

stacks/status-page/terragrunt.hcl

@@ -0,0 +1,8 @@
+include "root" {
+  path = find_in_parent_folders()
+}
+
+dependency "infra" {
+  config_path  = "../infra"
+  skip_outputs = true
+}