fix: poll hatasına zaman damgası ekle + STT'yi panelden kapatılabilir yap

- lastPollErrors artık {message, at} tutuyor — panelde hangi hatanın ne
  zaman oluştuğu görünmüyordu, eski/güncel ayrımı yapılamıyordu.
- "This live event will begin in N minutes" gibi zararsız mesajlar da
  hata rozetine düşüyordu, "is not currently live" ile aynı gruba alındı.
- Yeni stt_enabled ayarı (Ayarlar sayfası): kapatılınca stt_scoring.py
  OpenAI Whisper çağrısı yapmadan adayı PENDING_STT'de bırakıp çıkıyor —
  konuşmasız/ambiyans yayınlarda (bkz. NASA testi) boşa API maliyeti
  önleniyor.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/api-daemon/src/youtubePolling.ts

@@ -10,9 +10,18 @@ const execFileAsync = promisify(execFile);
 
 /**
  * Live detection failures are kept per channel and surfaced via GET /status
- * for debugging.
+ * for debugging. `at` lets the panel show how stale an error is — a message
+ * on its own doesn't say whether it's from the last poll or from hours ago
+ * before the channel started passing again.
  */
-export const lastPollErrors = new Map<string, string>();
+export interface PollError {
+  message: string;
+  at: string;
+}
+export const lastPollErrors = new Map<string, PollError>();
+
+/** Non-error outcomes yt-dlp still reports as a non-zero exit — not worth surfacing as a scary error badge in the panel. */
+const BENIGN_POLL_MESSAGE = /is not currently live|will begin in/;
 
 /**
  * A few approaches were tried before landing here:
@@ -57,11 +66,10 @@ async function findLiveVideoId(channelId: string): Promise<string | null> {
     return videoId || null;
   } catch (err) {
     const message = err instanceof Error ? err.message : String(err);
-    // yt-dlp reports "not live" as a non-zero exit too — that's a normal,
-    // expected outcome on every check where the channel isn't broadcasting,
-    // not a failure worth surfacing as an error in the panel.
-    if (!/is not currently live/.test(message)) {
-      lastPollErrors.set(channelId, message.slice(0, 500));
+    // yt-dlp reports "not live" / "starts in N minutes" as a non-zero exit
+    // too — normal, expected outcomes, not failures worth a red badge.
+    if (!BENIGN_POLL_MESSAGE.test(message)) {
+      lastPollErrors.set(channelId, { message: message.slice(0, 500), at: new Date().toISOString() });
     } else {
       lastPollErrors.delete(channelId);
     }
@@ -107,7 +115,7 @@ export async function startCaptureSession(
 /** Runs the live-check for a single channel and applies its result — the unit both `pollOnce` and the panel's manual "şimdi kontrol et" action reuse. */
 export async function checkChannel(channel: { id: string; name: string; channelId: string }): Promise<{
   liveVideoId: string | null;
-  error: string | null;
+  error: PollError | null;
 }> {
   const liveVideoId = await findLiveVideoId(channel.channelId);
   await prisma.channel.update({