refac: runtime settings are read once at startup and passed in through the composition root; no handler, router or repository reads environment variables

test/write_not_found_errors_test.go

@@ -144,7 +144,7 @@ func TestTheImageRepositoryReportsAMissingImageAsADomainErrorOnDelete(t *testing
 	if err := db.Create(&models.Image{Path: "/static/uploadedImages/one.png"}).Error; err != nil {
 		t.Fatalf("failed to seed image: %v", err)
 	}
-	repo := persistence.NewImageRepository(db)
+	repo := persistence.NewImageRepository(db, t.TempDir())
 
 	err := repo.Delete(9)
 	assertWriteResultIsImageNotFound(t, err)