feat: add MinIO presign endpoints to scraper API and SvelteKit presign helper

scraper/internal/storage/store.go

@@ -121,4 +121,12 @@ type Store interface {
 
 	// AudioObjectKey returns the MinIO object key for a cached audio file.
 	AudioObjectKey(slug string, n int, voice string, speed float64) string
+
+	// ── Presigned URLs ─────────────────────────────────────────────────────
+
+	// PresignChapter returns a presigned GET URL for a chapter markdown object.
+	PresignChapter(ctx context.Context, slug string, n int, expires time.Duration) (string, error)
+
+	// PresignAudio returns a presigned GET URL for an audio object.
+	PresignAudio(ctx context.Context, key string, expires time.Duration) (string, error)
 }