fix(server): refuse cross-site requests on the terrain-heights route

Follow-up to #686 requested on #923. The route's per-client limiter keys on the socket address, which for a cross-site <img> is the visitor's own browser, so any web page could fill the bounded cache with junk keys and spend the visitor's 90/min quota, leaving the app's own terrain lookups on 429. Gate the route with admitSameSite before the limiter, like the Places routes.

Co-authored-by: daikaginza <[email protected]>

scripts/package-boundaries.json

@@ -113,7 +113,9 @@
       "server/providers/terrain.js",
       "src/data/terrainHeightsProxy.js",
       "server/providers/common/rate-limit.js",
-      "src/sources/rateLimit.js"
+      "src/sources/rateLimit.js",
+      "server/providers/common/same-site.js",
+      "src/localRequestGate.mjs"
     ],
     "external": []
   },