Fix Stop Transcription button not updating after click

After calling POST /api/stop, the button stayed on "Stop Transcription"
because the state update depended on the WebSocket broadcast which can
be delayed or missed (event loop threading issue).

Fix: poll GET /api/status immediately after start/stop API calls to
update the UI state directly, rather than waiting for the WebSocket.

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

src/lib/components/Controls.svelte

@@ -17,6 +17,9 @@
       } else {
         await backendStore.apiPost("/api/start");
       }
+      // Poll status to update UI immediately instead of waiting
+      // for WebSocket broadcast (which can be delayed or missed)
+      await backendStore.pollStatus();
     } catch (err) {
       console.error("Failed to toggle transcription:", err);
     } finally {

src/lib/stores/backend.svelte.ts

@@ -302,6 +302,7 @@ export const backendStore = {
   setPort,
   connect: connectWebSocket,
   disconnect,
+  pollStatus,
   apiUrl,
   apiFetch,
   apiGet,