Note UX polish: pin marker, icon picker, fix Save button color

- The clicked location now stays marked (a plain maplibre-gl Marker,
  removed on save/cancel/deactivate) while the note form is open —
  before, nothing on the map showed where the pending note would land.
- POI_ICONS gains a dozen more symbols (water, dump station, toilets,
  playground, viewpoint, swimming, fishing, climbing, hiking, …) via
  Object.assign after PARK4NIGHT_TAGS' own icon constants are declared
  (they're below POI_ICONS in the file, so the literal itself can't
  reference them directly) — reused as real marker-badge glyphs, not
  just PARK4NIGHT_TAGS' inline description-tag icons. NoteSaveForm
  gets a picker grid for these, shown only for a Point note (a
  Measure-drawn line/polygon has no one spot for a badge).
- Fixed: .notes-panel__save's blue background was losing to
  .notes-panel__actions button's gray — same class-vs-class+element
  specificity trap .gpx-panel__action[hidden] already has a comment
  about elsewhere in this file. The button was never actually blue.

Verified live (properly simulating a logged-in session this time, via
Page.addScriptToEvaluateOnNewDocument rather than a post-load DOM
poke, since NotesControl's mount decision happens once, synchronously,
at page load): marker appears and clears correctly, 19 icons + "none"
render and select, Save renders #1a5fb4. Full suite: 115 runs, 0
failures.

TODO.adoc

@@ -47,6 +47,9 @@ independence from connectivity.
 ** [x] Fixed: a note saved before `properties.id` existed (the earliest test notes) had no Edit/Delete-able target — the popup no longer offers them without an id, and `rake gpx:backfill_note_ids` assigns one to any pre-existing Note feature missing it
 ** [x] Title + body split (name in the black header, body in a separate field) with light self-authored markdown (`**bold**`, `*italic*`, auto-linked URLs) in the body — a *new*, separate `formatNoteBody` (not `formatDescription`, which stays plain/untrusted-safe for uploaded GPX/park4night content per docs/nps-resources.adoc's earlier markdown-rendering call)
 ** [x] Gated behind login: NotesControl isn't added to the map at all when logged out, Measure's "Save as note" button is hidden (Measure itself stays usable either way)
+** [x] The clicked point stays marked on the map while the note form is open (a plain `Marker`, removed on save/cancel/deactivate) — it was disappearing back into the flat map with nothing showing where the note would land
+** [x] Icon picker for point notes (a grid in the save form) — extends `POI_ICONS` with more of the symbols `PARK4NIGHT_TAGS` already vendors (water, dump station, toilets, playground, viewpoint, swimming, fishing, climbing, hiking, …), reusable as real marker-badge glyphs, not just inline tag icons. Hidden for a Measure-drawn line/polygon note — no single spot for a badge to sit at
+** [x] Fixed: the Save button's own blue background was losing to `.notes-panel__actions button`'s gray — same class-vs-class+element specificity trap as `.gpx-panel__action[hidden]` already has a comment about elsewhere in this file, just not yet applied here
 ** [ ] The Unigrid Matrix category filter only re-slices the *points* source (`_applyCategoryFilter`) — toggling the "Note" category off hides point notes but not polygon/line ones sharing that category
 * [ ] Offline satellite tile caching (e.g. ESRI) for a selected route area — key for judging surface quality and obstacles when wild camping