feat: add S2 GhostMaps live intel layer

Adds an "S2 GhostMaps" layer (Events group) that renders S2 Underground's
GhostMaps KMZ exports (Common Intelligence Picture, Kinetic 30d, Border
Crisis, Iran CIP/Kinetic, Yemen FLOT, latest incident drop).

- server/providers/ghostMaps.js: watcher polls the repo's git smart-HTTP
  ref advertisement (default every 15s, GHOSTMAPS_POLL_SECONDS), fetches
  the tree only on a new head, caches commit-pinned files by blob sha and
  pushes catalog updates to browsers over SSE (/api/ghostmaps/events).
- src/layers/ghostMaps: KML reader, ArcGIS popup-table parsing, per-product
  data sources, product chips, horizon-culled pins, report cards.
- Unit tests, QA gate (scripts/qa-ghostmaps.mjs), credits (CC BY-NC-SA 4.0),
  i18n, voice manifest, layer-state token 5.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/data/dataCredits.js

@@ -441,6 +441,14 @@ export const DATA_CREDITS = [
       '(<a href="https://earthdata.nasa.gov/firms" target="_blank" rel="noopener">earthdata.nasa.gov/firms</a>), ' +
       'part of NASA’s Earth Observing System Data and Information System (EOSDIS)',
   },
+  {
+    key: 's2-ghostmaps',
+    html:
+      'S2 GhostMaps intel products: S2 Underground © by S2A1, ' +
+      '<a href="https://github.com/s2underground/GhostMaps" target="_blank" rel="noopener">github.com/s2underground/GhostMaps</a>, ' +
+      'licensed under <a href="https://creativecommons.org/licenses/by-nc-sa/4.0/" target="_blank" rel="noopener">CC BY-NC-SA 4.0</a>. ' +
+      'Shown as published; reports are S2 assessments, not verified fact.',
+  },
   {
     key: 'drivebc-cctv',
     html: