Fix image signed URLs ignoring updated public base URL.

Resolve public_base_url at SignURL time so admin settings apply without restart.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/storage/imagestore/store.go

@@ -17,15 +17,22 @@ import (
 )
 
 type Store struct {
-	db       *gorm.DB
-	baseDir  string
-	signKey  string
-	publicURL string
-	ttl      time.Duration
+	db        *gorm.DB
+	baseDir   string
+	signKey   string
+	publicURL func() string
+	ttl       time.Duration
 }
 
-func New(db *gorm.DB, baseDir, publicURL, signKey string, ttl time.Duration) *Store {
-	return &Store{db: db, baseDir: baseDir, publicURL: strings.TrimRight(publicURL, "/"), signKey: signKey, ttl: ttl}
+func New(db *gorm.DB, baseDir string, publicURL func() string, signKey string, ttl time.Duration) *Store {
+	return &Store{db: db, baseDir: baseDir, publicURL: publicURL, signKey: signKey, ttl: ttl}
+}
+
+func (s *Store) baseURL() string {
+	if s.publicURL == nil {
+		return ""
+	}
+	return strings.TrimRight(s.publicURL(), "/")
 }
 
 func (s *Store) EnsureDir() error {
@@ -76,7 +83,7 @@ func (s *Store) ListByPrediction(predictionID string) ([]model.StoredImage, erro
 func (s *Store) SignURL(imageID string) string {
 	exp := time.Now().Add(s.ttl).Unix()
 	sig := s.sign(imageID, exp)
-	return fmt.Sprintf("%s/files/%s?exp=%d&sig=%s", s.publicURL, imageID, exp, sig)
+	return fmt.Sprintf("%s/files/%s?exp=%d&sig=%s", s.baseURL(), imageID, exp, sig)
 }
 
 func (s *Store) Verify(imageID string, exp int64, sig string) bool {