feat(store): TranscriptStatus read field + status setter/loader

Surfaces videos.transcript_status (migration 007) on SummaryRow and adds
SetTranscriptStatus / GetTranscriptStatus / RateLimitedVideoIDs.

SetTranscriptStatus is the single choke point for the rate-limit lifecycle:
"rate_limited" stamps rate_limited_at = NOW(), every other status clears it,
so the runner's backoff window and the UI badge read one consistent source.
RateLimitedVideoIDs is the per-pass loader (mirrors SeenVideoIDs) the runner
uses to skip still-throttled videos without re-hitting the caption endpoint.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/adapters/store/reads.go

@@ -49,6 +49,10 @@ type SummaryRow struct {
 	// set by the web "Summarize" button and cleared by the next `tapir run`. Only
 	// populated by ListVideos/GetVideoRow (summary-only reads leave it false).
 	SummarizeRequested bool
+	// TranscriptStatus mirrors videos.transcript_status (migration 007): "" (unset),
+	// "none", "rate_limited", or "fetched". Drives the "Retrying later" list badge.
+	// Only populated by ListVideos/GetVideoRow ("" on summary-only reads).
+	TranscriptStatus string
 }
 
 // selectSummary is the shared projection for both reads. videos is LEFT JOINed
@@ -132,7 +136,8 @@ const selectVideo = `
 	       COALESCE(s.fallback_used, FALSE),
 	       COALESCE(s.created_at, v.seen_at),
 	       (s.id IS NOT NULL) AS summarized,
-	       v.summarize_requested
+	       v.summarize_requested,
+	       COALESCE(v.transcript_status, '')
 	  FROM videos v
 	  LEFT JOIN summaries s ON s.video_id = v.id AND s.user_id = v.user_id`
 
@@ -245,6 +250,7 @@ func scanVideoRow(rows pgx.Row) (SummaryRow, error) {
 		&row.CreatedAt,
 		&row.Summarized,
 		&row.SummarizeRequested,
+		&row.TranscriptStatus,
 	); err != nil {
 		return SummaryRow{}, fmt.Errorf("store: scan video: %w", err)
 	}