feat: add military bases map layer for Western Pacific

Add 18 US military bases (Japan, Guam, South Korea, Hawaii, Diego Garcia)
as a toggleable map layer. Follows the existing data center layer pattern:
static JSON → backend fetcher → slow-tier API → frontend GeoJSON layer.

Includes red circle markers with labels, click popups showing operator
and branch info, and a toggle in the left panel.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/app/page.tsx

@@ -162,6 +162,7 @@ export default function Dashboard() {
     firms: false,
     internet_outages: false,
     datacenters: false,
+    military_bases: false,
   });
 
   // NASA GIBS satellite imagery state