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/js/gpx.js

@@ -60,8 +60,17 @@ export class GpxPanelControl {
 
     // notes.js writes directly into the same GPX store (a hand-drawn note
     // saved into a .geojson layer) — refresh so a newly created/grown file
-    // shows up in the tree without a manual reopen.
-    onGpxStoreChanged(() => this._loadTree());
+    // shows up in the tree without a manual reopen, and auto-show it (check
+    // + render) since a note the user just placed being invisible until
+    // they find and check its layer by hand defeats the point of dropping
+    // a pin right there on the map.
+    onGpxStoreChanged((path) => {
+      if (path) {
+        this._visible.add(path);
+        this._reloadFile(path);
+      }
+      this._loadTree();
+    });
   }
 
   // Registered once, always white, as plain (non-SDF) images: these used to