fix: update Backrest config version to 4 for compatibility

Changed config version from 1 to 4 to match Backrest 1.10.1
requirements. Version 1 is too old and requires migration through
intermediate version 1.4.0.

Config now loads successfully with all 11 backup plans scheduled.

restic/config.json

@@ -1,5 +1,5 @@
 {
-  "version": 1,
+  "version": 4,
   "instance": "falcon",
   "repos": [
     {