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

scraper/internal/storage/minio.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"strings"
+	"time"
 
 	"github.com/minio/minio-go/v7"
 	"github.com/minio/minio-go/v7/pkg/credentials"
@@ -165,6 +166,29 @@ func (m *MinioClient) AudioExists(ctx context.Context, key string) bool {
 	return err == nil
 }
 
+// ─── Presigned URLs ───────────────────────────────────────────────────────────
+
+// PresignChapter returns a presigned GET URL for a chapter object, valid for
+// the given duration. The URL is signed with the MinIO credentials and can be
+// fetched directly by the browser without authentication.
+func (m *MinioClient) PresignChapter(ctx context.Context, slug string, vol, n int, expires time.Duration) (string, error) {
+	key := chapterKey(slug, vol, n)
+	u, err := m.c.PresignedGetObject(ctx, m.cfg.BucketChapters, key, expires, nil)
+	if err != nil {
+		return "", fmt.Errorf("minio: presign chapter %s: %w", key, err)
+	}
+	return u.String(), nil
+}
+
+// PresignAudio returns a presigned GET URL for an audio object.
+func (m *MinioClient) PresignAudio(ctx context.Context, key string, expires time.Duration) (string, error) {
+	u, err := m.c.PresignedGetObject(ctx, m.cfg.BucketAudio, key, expires, nil)
+	if err != nil {
+		return "", fmt.Errorf("minio: presign audio %s: %w", key, err)
+	}
+	return u.String(), nil
+}
+
 // ─── helpers ──────────────────────────────────────────────────────────────────
 
 // sanitiseVoice converts a voice name to a filename-safe string.