Fix note UX: unreachable wiki link, white Save hover, stale icon preview, invisible new points

- "Nearby on Wikipedia" linked to KIWIX_URL, a Docker-internal hostname
  (http://kiwix:8080) no real browser can resolve. Split it: KIWIX_URL
  stays server-side-only for the reachability check, and the link
  itself is built from KIWIX_PUBLIC_PORT (kiwix-serve's newly
  published host port) plus whatever host the visitor already used to
  reach maptool — works regardless of which hostname/IP that is.
- The Save button went white on hover in GTK-themed Chrome: the
  browser's native button skin was painting over the custom
  background because appearance wasn't reset.
- The map preview marker for a pending note always showed a plain red
  pin no matter which icon was picked in the form. NoteSaveForm now
  reports icon changes via onIconChange so NotesControl can update the
  marker's glyph live.
- Saving a note (or a Measure "Save as note") left the new/grown
  .geojson file unchecked and invisible until manually toggled on.
  notifyGpxStoreChanged now carries the affected path so
  GpxPanelControl auto-shows it.

public/css/style.css

@@ -930,6 +930,29 @@ html, body {
   background: #dbe9ff;
 }
 
+/* The pending-note marker shown on the map while the save form is open —
+   updates live to whatever icon is picked (see notes.js's onIconChange). A
+   plain round badge (not a drop-pin shape) since MapLibre anchors a custom
+   marker element at its center, and a pin's usual tip-points-at-the-spot
+   shape needs a bottom anchor to line up correctly. */
+.notes-panel__preview-marker {
+  width: 26px;
+  height: 26px;
+  border-radius: 50%;
+  background: #c0392b;
+  border: 2px solid #fff;
+  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.4);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  color: #fff;
+}
+
+.notes-panel__preview-marker svg {
+  width: 15px;
+  height: 15px;
+}
+
 .notes-panel__target,
 .notes-panel__new-name {
   width: 100%;
@@ -948,6 +971,11 @@ html, body {
 }
 
 .notes-panel__actions button {
+  /* Without this, some browsers (GTK-themed Chrome on Linux in
+     particular) paint their own native hover/active highlight over a
+     button's background instead of leaving a custom one alone — the
+     Save button visibly went white on hover because of exactly this. */
+  appearance: none;
   width: auto;
   height: auto;
   padding: 4px 10px;