Merge origin/main: resolve conflicts in CLI surface, --prune, helpers

- Adopt origin's SnapshotPurgeOptions naming and PurgeSnapshotsWithOptions
  method, but extend with Names []string (repeatable --snapshot flag) and
  Quiet bool for use by --prune.
- Adopt origin's parseSnapshotName helper.
- Fold the duplicate post-backup prune block into one runPostBackupPrune
  call that filters retention to the snapshot names just backed up.
- Keep the shallow-verify timestamp parsing fix and the dead deep-verify
  branch removal; use origin's printVerifyHeader/verifyManifestBlobsExist
  helper extraction.
- Drop top-level vaultik purge and verify (duplicates of snapshot purge
  and snapshot verify).
- Drop the resurrected daemon block from info.go (config fields no
  longer exist).
- Combine Makefile targets: gofmt -l for fmt-check, -race for tests,
  release/release-snapshot/docker/hooks/deps/test-coverage all included.

go.mod

@@ -1,6 +1,6 @@
 module git.eeqj.de/sneak/vaultik
 
-go 1.24.4
+go 1.26.1
 
 require (
 	filippo.io/age v1.2.1
@@ -23,6 +23,7 @@ require (
 	github.com/spf13/cobra v1.10.1
 	github.com/stretchr/testify v1.11.1
 	go.uber.org/fx v1.24.0
+	golang.org/x/sync v0.18.0
 	golang.org/x/term v0.37.0
 	gopkg.in/yaml.v3 v3.0.1
 	modernc.org/sqlite v1.38.0
@@ -265,7 +266,6 @@ require (
 	golang.org/x/exp v0.0.0-20251023183803-a4bb9ffd2546 // indirect
 	golang.org/x/net v0.47.0 // indirect
 	golang.org/x/oauth2 v0.33.0 // indirect
-	golang.org/x/sync v0.18.0 // indirect
 	golang.org/x/sys v0.38.0 // indirect
 	golang.org/x/text v0.31.0 // indirect
 	golang.org/x/time v0.14.0 // indirect