Split notes into a title + body, with light self-authored markdown

Both NoteSaveForm (create) and the popup's inline Edit form now have
a title input (-> properties.name, shown in the black header, same as
every other waypoint popup) and a separate body textarea (->
properties.description) for more detail than a single line.

New formatNoteBody renders that body with a small self-rolled
markdown subset — **bold**, *italic*, auto-linked URLs (reusing the
existing linkify), newlines to <br> — deliberately a new function, not
a change to formatDescription: that one renders uploaded GPX/park4night
content, which is untrusted, and docs/nps-resources.adoc already has a
specific call not to add markdown rendering to that path. A note's
body is written by the logged-in viewer themselves, not uploaded, so
that concern doesn't apply here — the escape-then-selectively-markup
order (linkify first, since it does its own escaping, then wrap
already-escaped text in real <strong>/<em> tags) keeps it safe either
way.

Verified live: title renders in the popup header, **bold**/*italic*/
a URL in the body all render correctly. Full test suite: 115 runs, 0
failures (unaffected — description is just another property, not
something the backend routes inspect).

public/css/style.css

@@ -869,7 +869,8 @@ html, body {
   display: none;
 }
 
-.notes-panel__text {
+.notes-panel__title,
+.notes-panel__body {
   width: 100%;
   box-sizing: border-box;
   font: inherit;
@@ -877,6 +878,13 @@ html, body {
   padding: 4px 6px;
   border: 1px solid #ddd;
   border-radius: 4px;
+}
+
+.notes-panel__title {
+  font-weight: 600;
+}
+
+.notes-panel__body {
   resize: vertical;
 }
 
@@ -1053,7 +1061,8 @@ html, body {
   color: #fff;
 }
 
-.gpx-popup__edit-text {
+.gpx-popup__edit-title,
+.gpx-popup__edit-body {
   width: 100%;
   box-sizing: border-box;
   font: inherit;
@@ -1061,6 +1070,14 @@ html, body {
   padding: 4px 6px;
   border: 1px solid #ddd;
   border-radius: 4px;
+  margin-bottom: 6px;
+}
+
+.gpx-popup__edit-title {
+  font-weight: 600;
+}
+
+.gpx-popup__edit-body {
   resize: vertical;
 }