feat(rust): the live map draws monuments by label, minor labels hidden (PLAN_REDESIGNS §4, D196)

A switch per monument label, a fleet default and a per-server override, on
Admin -> Rust visibility's live map card. Substations, caves, train tunnels,
wells and the other minor labels start hidden; every other label is drawn,
so a monument a game update adds appears. GET /map leaves hidden labels out
of the answer, so the website and the app both lose them.

No schema change: rows are map.marker.<label key> in rust_settings and
rust_map_overrides. No wire change.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

server/router/public/rust.controller.js

@@ -264,7 +264,8 @@ async function getMap(req, res) {
           }
         : null,
       geometry: map.geometryOf(row),
-      ...(acc.layers.world.visible ? { monuments: map.monumentsOf(row) } : {}),
+      // D196: only the labels drawn on this server; a hidden label is not sent at all.
+      ...(acc.layers.world.visible ? { monuments: map.filterMonuments(map.monumentsOf(row), acc.markers) } : {}),
       layers: acc.layers,
       // `signedIn` is what lets the page offer "link your Steam account" to the
       // person who can act on it, and not to a visitor who has no account at all.