Embed server browser as main menu modal

Refactors the browser UI into a reusable `CO_Browser.create()` module and adds embedded modal styling so MULTIPLAYER opens inside the main menu instead of swapping to a separate view. Updates main-menu JS/CSS to host, animate, and route input for the browser panel while keeping nav and prompts in sync. On the C++ side, PrismaUI now drives browser show/hide and event dispatch through the main menu view, and `ServerBrowserBridge::SetView()` was added so bridge events target the active host view.

ui/views/CommonwealthOnline/main-menu/styles.css

@@ -406,3 +406,32 @@ body {
     ),
     rgba(4, 8, 6, 0.32);
 }
+
+/* Browser mode: keep main nav, dim background more */
+
+.main-screen.is-browser-mode .left-panel {
+  overflow: hidden;
+  background:
+    linear-gradient(
+      90deg,
+      rgba(8, 14, 10, 0.9) 0%,
+      rgba(8, 14, 10, 0.78) 65%,
+      rgba(8, 14, 10, 0.15) 100%
+    );
+}
+
+.main-screen.is-browser-mode .menu-item__bar {
+  width: calc(100% + 28px * var(--co-ui-scale));
+}
+
+.main-screen.is-browser-mode .scene-overlay {
+  background:
+    linear-gradient(
+      90deg,
+      rgba(6, 10, 8, 0.88) 0%,
+      rgba(6, 10, 8, 0.55) 24%,
+      rgba(6, 10, 8, 0.4) 55%,
+      rgba(6, 10, 8, 0.48) 100%
+    ),
+    rgba(4, 8, 6, 0.32);
+}