Give Overpass POI downloads icons/descriptions and unique filenames

Overpass categories now carry the same icon+color styling a p4n2gpx
waypoint gets, instead of falling back to gpx.js's plain red marker,
plus a popup description built from opening_hours/operator/website
tags. Supermarket/convenience store reuse NPS's generic store glyph,
the only honest match in that icon set.

Each plugin run's saved filename now bakes in the area's center and a
timestamp, so repeated downloads for different areas land as separate,
identifiable files instead of overpass-pois.geojson/-1/-2/...

public/js/icons.js

@@ -155,6 +155,20 @@ const BICYCLE_TRAIL_ICON = `
 		c1,0,1,1.3,0,1.3H13.1L13.1,9.8z"/>
 </svg>`;
 
+// src/store-22.svg — NPS's generic shop pictogram, the closest match in
+// their set for both a supermarket and a convenience store (no separate
+// grocery-specific glyph exists there).
+const STORE_ICON = `
+<svg viewBox="0 0 22 22" fill="currentColor">
+<path d="M20,9c0,0-0.8,3-4,3C16,12,15.8,9.9,20,9z"/>
+<path d="M17,14.3c0.5-0.5,1.3-0.9,2.1-0.9c1.6,0,2.9,1.3,2.9,3v0.2l0,0c-0.1,0.6-0.3,1.5-0.7,2.4c0,0-0.8,1.6-1.5,2.3l-0.1,0.1
+	c-0.3,0.3-0.8,0.5-1.3,0.5c-0.6,0-1.1-0.5-1.5-1c-0.3,0.5-0.9,1-1.5,1c-0.5,0-0.9-0.2-1.3-0.5L14,21.3c-0.7-0.7-1.5-2.3-1.5-2.3
+	c-0.5-1-0.7-1.8-0.7-2.4l0,0v-0.2c0-1.7,1.3-3,2.9-3C15.7,13.5,16.5,13.8,17,14.3"/>
+<polygon points="4,0 8,0 8,2 4,2 	"/>
+<path d="M7,3H3c0,0-0.7,0.2-1.2,0.7L0.2,5.8C0.1,6,0,5.9,0,6.1V21c0,0.4,0.6,1,1,1h8c0.4,0,1-0.6,1-1V6C10,6,9.6,3.3,7,3z M4,4v5H3
+	v1H2l-1,1v-1V6h1V5h1L4,4z"/>
+</svg>`;
+
 export const POI_ICONS = {
   // src/parking-22.svg
   amenity_parking: `
@@ -335,6 +349,8 @@ Object.assign(POI_ICONS, {
   leisure_fishing: FISHING_ICON,
   sport_climbing: CLIMBING_ICON,
   route_hiking: WALKING_ICON,
+  shop_supermarket: STORE_ICON,
+  shop_convenience: STORE_ICON,
 });
 
 export const LIVETRACK_ICON = `