Show notes from similar earlier incidents

Each incident gets a signature: the alert name plus the group labels that
say what is broken, minus the ones that only say where it ran (instance,
pod, container, ...). GET /api/incidents/{id}/similar returns resolved
incidents in the same team with the same signature that have notes.

Notes can be marked as the resolution note, "what fixed it", either with a
resolution field on resolve or pinned on a note. Those lead the similar
list, show on the incident page as "Seen before", and the triggered
notification carries the latest one.

Claude-Session: https://claude.ai/code/session_01MMados3BD1oSjevHxbmVqU

internal/web/static/app.css

@@ -450,11 +450,16 @@ details[open] > summary { margin-bottom: 8px; }
 .tl-text { overflow-wrap: anywhere; }
 .tl-text .who { font-weight: 650; }
 .tl-time { color: var(--faint); font-size: 12px; }
-.tl-note .note {
+.note {
   margin-top: 6px; padding: 10px 12px;
   background: var(--surface-2); border-radius: var(--radius-sm);
   white-space: pre-wrap; overflow-wrap: anywhere;
 }
+.note-fix { background: var(--ok-soft); border-left: 3px solid var(--ok); }
+.similar { list-style: none; margin: 0; padding: 0; }
+.similar-item { padding: 10px 0; }
+.similar-item + .similar-item { border-top: 1px solid var(--border, var(--surface-2)); }
+.check { display: flex; align-items: center; gap: 8px; font-size: 14px; color: var(--muted); }
 .note-actions { display: flex; justify-content: flex-end; }
 .note-actions .btn { color: var(--muted); }