fix(ui): compute activeModel via $derived instead of invalid {@const} placement (T8.7)

src/lib/views/Settings.svelte

@@ -47,6 +47,10 @@
     "recording" | "hardware" | "storage" | "calendar" | "sync" | "ai" | "mcp" | "privacy" | "about"
   >("recording");
 
+  // The currently active whisper model (T8.7, FR-TRX-4) — gates the
+  // language picker below (multilingual model required).
+  let activeModel = $derived(settings.models.find((m) => m.active));
+
   // ---- About (version + build commit + source) ----
   const SOURCE_URL = "https://git.dou.bet/iamdoubz/WhispAssist";
   let appInfo = $state<{ version: string; commit: string } | null>(null);
@@ -798,7 +802,6 @@
         </ul>
 
         <h4>Transcription Language</h4>
-        {@const activeModel = settings.models.find((m) => m.active)}
         {#if activeModel?.multilingual}
           <label
             >Language