feat: add GPS/GNSS jamming map layer + CII integration (#570)

* feat: add GPS/GNSS jamming data ingestion from gpsjam.org

- scripts/fetch-gpsjam.mjs: standalone fetcher that downloads daily H3
  hex data, filters medium/high interference, converts to lat/lon via
  h3-js, and writes JSON. Can be run on cron.
- api/gpsjam.js: Vercel Edge Function that proxies gpsjam.org data with
  1hr cache, returns medium/high hexes for frontend consumption.
- src/services/gps-interference.ts: frontend service that fetches from
  the Edge API, converts H3→lat/lon, and classifies by conflict region.
- h3-js added as dependency for hex→coordinate conversion.

* feat: add GPS jamming map layer, CII integration, and country brief signals

Wire gpsjam.org data into map visualization, instability scoring, and
country intelligence. ScatterplotLayer renders high (red) and medium
(orange) interference hexes. CII security score incorporates jamming
counts per country via h3→country geocoding with cache. Country briefs
show jamming zone chip. Full i18n across 18 locales including popup
labels. Data loads with intelligence signals cycle (15min), gated by
1hr client-side cache.

.gitignore

@@ -37,3 +37,4 @@ scripts/data/pizzint-processed.json
 scripts/data/osm-military-processed.json
 scripts/data/military-bases-final.json
 scripts/data/dedup-dropped-pairs.json
+scripts/data/gpsjam-latest.json