make REUSE compliant

templates/seaf-daemon.service.j2

@@ -1,3 +1,7 @@
+# SPDX-FileCopyrightText: 2023 Max Mehl <https://mehl.mx>
+#
+# SPDX-License-Identifier: Apache-2.0
+
 [Unit]
 Description=Seafile Daemon
 After=network.target

templates/seafile_mirror.conf.yaml.j2

@@ -1 +1,5 @@
+# SPDX-FileCopyrightText: 2023 Max Mehl <https://mehl.mx>
+#
+# SPDX-License-Identifier: Apache-2.0
+
 {{seafile_syncs|to_yaml(sort_keys=False)}}