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>

steward/templates/base.html

@@ -43,6 +43,7 @@
         <div class="nav-group-label">Overview</div>
         <a href="/" {% if _p == '/' %}class="active" aria-current="page"{% endif %}>Dashboard</a>
         <a href="/timeline/" {% if _p.startswith('/timeline') %}class="active" aria-current="page"{% endif %}>Timeline</a>
+        <a href="/tickets/" {% if _p.startswith('/tickets') %}class="active" aria-current="page"{% endif %}>Tickets</a>
       </div>
       <div class="nav-group">
         <div class="nav-group-label">Infrastructure</div>