chore: добавить SLM-каркас admin

- добавлен app entrypoint, main layout и dashboard screen\n- настроены алиасы SLM-слоёв и PostCSS для CSS Modules\n- перенесены глобальные стили в shared/styles

apps/admin/src/app/app.tsx

@@ -0,0 +1,10 @@
+import { MainLayout } from "layouts/main"
+import { DashboardScreen } from "screens/dashboard"
+
+export function App() {
+  return (
+    <MainLayout>
+      <DashboardScreen />
+    </MainLayout>
+  )
+}

apps/admin/src/app/main.tsx

@@ -0,0 +1,18 @@
+import "shared/styles/global.css"
+
+import { StrictMode } from "react"
+import { createRoot } from "react-dom/client"
+
+import { App } from "./app"
+
+const root = document.getElementById("root")
+
+if (!root) {
+  throw new Error("Root element #root not found")
+}
+
+createRoot(root).render(
+  <StrictMode>
+    <App />
+  </StrictMode>,
+)