feat: add LiteLLM health page to dashboard

Expose LiteLLM operational status in the NAS Dashboard UI so auth-required and outage states are visible without calling backend APIs directly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

dashboard/frontend/src/App.svelte

@@ -9,6 +9,7 @@
   import Settings from "./routes/Settings.svelte";
   import ChatSummary from "./routes/ChatSummary.svelte";
   import Security from "./routes/Security.svelte";
+  import LiteLLM from "./routes/LiteLLM.svelte";
   import Login from "./routes/Login.svelte";
   import { onMount } from "svelte";
   import { getToken, checkAuth, setToken, setRefreshToken, currentUser, setCurrentUser, getPreferences, savePreferences } from "./lib/api.js";
@@ -153,6 +154,8 @@
           <Settings />
         {:else if page === "security" && hasPageAccess("security")}
           <Security />
+        {:else if page === "litellm" && hasPageAccess("dashboard")}
+          <LiteLLM />
         {:else}
           <Dashboard />
         {/if}