Cyberpunk visual overhaul

Dark CARTO basemap (was default bright OSM tiles), Orbitron/Share Tech
Mono fonts, neon cyan/magenta HUD chrome with glassmorphism panels,
glowing divIcon portal markers (pulsing when claimed) replacing plain
circle dots, neon drop-shadow filters on links/fields, and a subtle
scanline overlay. Login and team-pick screens restyled to match.

frontend/index.html

@@ -4,6 +4,12 @@
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>Regress</title>
+    <link rel="preconnect" href="https://fonts.googleapis.com" />
+    <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
+    <link
+      href="https://fonts.googleapis.com/css2?family=Orbitron:wght@500;700;900&family=Share+Tech+Mono&display=swap"
+      rel="stylesheet"
+    />
     <!-- No-op outside an Archipelago iframe (see nostr-provider.js's own
          window === window.top guard) — safe to always include. Provides
          window.nostr + auto sign-in via the node's selected nostr identity