docs(monitor): bump to v0.4.0, update app.md with Monitor + WS section

- About info updated to reflect Monitor as primary tab and the WS feature set.
- app.md gains a dedicated "Fase — Monitor tab + WebSocket live stream" section
  documenting the architecture, KPIs, WS hub design, fallback semantics, and
  the scope decisions (no TLS, skip Accept verification, WS client not yet
  extracted to cpp/functions/).
- Roadmap items added: extract ws_client when a second consumer arrives,
  Sec-WebSocket-Accept verification, migrate to coder/websocket on the server.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

main.cpp

@@ -262,11 +262,12 @@ int main(int argc, char** argv) {
     // Info de la ventana About (submenu Settings → About...)
     fn_ui::about_window_set_info(
         "fn_registry Dashboard",
-        "0.3.0",
-        "Dashboard ImGui para visualizar el estado del fn_registry. "
-        "Consume datos via sqlite_api HTTP (fallback a SQLite directo). "
-        "KPIs con sparkline, charts con leyenda, tablas, altura responsive, "
-        "Status panel en Settings, multi-viewport, dashboard_panel en views."
+        "0.4.0",
+        "Dashboard ImGui del fn_registry. Pestana Monitor por defecto con KPIs "
+        "live (Calls / Errors / Violations / Copies / Versions), Recent Executions "
+        "con timestamp, filtro de ventana (1h/24h/7d/30d/All) y WS subscription "
+        "al hub /api/events/call_monitor de sqlite_api. Resto de tabs (Dashboard, "
+        "Explorer, Projects, Apps, Analysis, Types) sin cambios."
     );
 
     // Seccion Status dentro de la ventana Settings (submenu Settings → Settings...).