Refactor server startup: elimina segfaults, añade leaflet-workaround

Retira import './segfaults' (workaround de crash obsoleto) y añade
leaflet-workaround.js (shims global window/document/navigator para
render de Leaflet en servidor). Ajustes menores en publications de
FalsePositives y subsUnion.

imports/startup/server/leaflet-workaround.js

@@ -0,0 +1,19 @@
+// imports/startup/server/leaflet-workaround.js
+global.window = {
+  screen: {
+    deviceXDPI: 1,
+    logicalXDPI: 1
+  }
+};
+global.document = {
+  documentElement: {
+    style: {}
+  },
+  createElement: () => {
+    return {};
+  }
+};
+global.navigator = {
+  userAgent: 'foo',
+  platform: 'bar'
+};