Add two filters to the /hikes filter panel:
- "Nur Touren in der aktuellen Saison" toggle — keeps only hikes whose
recommended season window covers the current month (year-wrap aware;
hikes without a window count as year-round).
- "Kanton / Land" — a typeahead that abstracts the hike's area over the
border: Swiss hikes group by canton (coat-of-arms), hikes abroad by
country (flag). Generalised the tag typeahead into ChipTypeahead
(optional icon + label mapping) and reused it for both tags and areas.
Supporting bits: countries.ts (ISO/name → flag), hikeArea.ts (the
canton-or-country resolver, namespaced so codes can't collide), prepared
flag SVGs for CH/DE/IT/AT/FR, and an optional `country` field on the hike
manifest type (populated by the build script; the app falls back to canton
for Swiss hikes until a rebuild).
