feat(tickets): open, comment and resolve tickets from the UI and MCP; known issues on alerts and anomalies (#6351, #6352)

A ticket records a known problem: title, area, hosts, subject, description,
links to alert rules and anomalies, and a log of comments, edits, resolving
and reopening. Opening, resolving (with the resolution as the note) and
reopening go on the timeline; every step is audited, and the audit rows stay
off the timeline.

An alert or anomaly an open ticket covers (by link, by subject, or a
host-wide ticket on the host itself) shows a Known issue badge, and offers
"Open a ticket" prefilled from its rule or anomaly when none does. Hosts,
monitors and containers get a Known issues card.

MCP: list_tickets, get_ticket (viewer); open_ticket, update_ticket,
comment_ticket, resolve_ticket, reopen_ticket (operator). list_alerts and
list_anomalies carry known_issue; get_overview, get_host, get_monitor and
get_container carry open_tickets. Also update_change and delete_change for
changes recorded by hand (author or admin).

Tickets are left out of backups, like the timeline (2026-10-15 ruling).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -121,6 +121,7 @@ See `docs/plugins/` for a full plugin development guide.
 | `docs/core/ansible.md` | Playbook sources, run lifecycle, SSE streaming |
 | `docs/core/backups.md` | Steward's daily backup to an S3 bucket (Fabled Archives), what it holds, and `steward restore` |
 | `docs/core/timeline.md` | The timeline: what it records from each source, areas and kinds, Settings → Timeline |
+| `docs/core/tickets.md` | Tickets: known problems, linked to alerts and anomalies, shown as known issues, resolved onto the timeline |
 | `docs/plugins/overview.md` | Plugin system: how loading works, plugin.yaml schema, required exports |
 | `docs/plugins/writing-a-plugin.md` | Step-by-step plugin development guide |
 | `docs/plugins/traefik.md` | Traefik plugin: config, metrics, alert rule examples |