Add the sick note document kind

A certificate of incapacity for work (in Germany the
Arbeitsunfähigkeitsbescheinigung) is now its own document kind,
SICK_NOTE, instead of Other. The enum value rides migration 0370.

Uploads, edits, the kind filter, bulk edits, the import script and the
backup format accept it; the vault files it with a thermometer glyph
between prescriptions and referrals; the filing suggestion can propose
it and names the words a sick note carries. The extraction's own kind
field keeps its three values.

scripts/import-documents.mjs

@@ -49,6 +49,7 @@ const KINDS = [
   "REFERRAL",
   "INSURANCE",
   "VACCINATION",
+  "SICK_NOTE",
   "OTHER",
 ];
 const TITLE_MAX = 200;