nfs-mirror: append transferred files to offsite-sync manifest

Step 1 of offsite-sync-backup is incremental on non-monthly days,
driven by /mnt/backup/.changed-files which only daily-backup wrote
to. nfs-mirror's writes were therefore invisible to Step 1 until the
next monthly --delete pass — which would *also* wipe data
pre-positioned on Synology pve-backup/ (e.g. the in-place btrfs
rename we just did to relocate ~160G of NFS subtrees from
/Backup/Viki/nfs/<svc>/ to /Backup/Viki/pve-backup/<svc>/).

Fix: snapshot a timestamp before rsync, then after rsync use
`find -newer $STAMP -type f -printf '%P\n'` to enumerate every file
nfs-mirror created/modified and append to the manifest. Paths are
relative to /mnt/backup/ (matches Step 1 --files-from expectation).
State files are excluded.

The current in-flight first run started before this patch was
deployed, so its writes won't auto-populate the manifest — a one-off
manual backfill will be done after it completes.

stacks/url/.terraform.lock.hcl

@@ -24,6 +24,22 @@ provider "registry.terraform.io/cloudflare/cloudflare" {
   ]
 }
 
+provider "registry.terraform.io/gavinbunney/kubectl" {
+  version     = "1.19.0"
+  constraints = "~> 1.14"
+  hashes = [
+    "h1:9QkxPjp0x5FZFfJbE+B7hBOoads9gmdfj9aYu5N4Sfc=",
+  ]
+}
+
+provider "registry.terraform.io/goauthentik/authentik" {
+  version     = "2024.12.1"
+  constraints = "~> 2024.10"
+  hashes = [
+    "h1:roBMd+gi+TGgikH/bMzEI8JfvJiMAQWt+8FmokCrQIs=",
+  ]
+}
+
 provider "registry.terraform.io/hashicorp/helm" {
   version = "3.1.1"
   hashes = [