v0.6.0: slice 6 Phase B — PBS offsite tier (verify + PBS-API client + reporting)

Spike-proven that backup/restore-to-PBS reuse Phase A unchanged; the only new code is
the verify capability, a small PBS-API client, and PBSSnapshot reporting.

- internal/pbs: fingerprint-pinned, token-authed PBS-API client (Verify/Snapshots/
  TaskStatus, node-from-UPID; secret read from /etc/pve/priv/storage/<id>.pw at runtime,
  never logged) + the verify maintenance loop (own cadence, default 6h, NOT gated/journaled,
  like the watchdog) + SnapshotStore.
- hub: PBSSnapshot filled (namespace/type/id/time/size/owner/protected/encrypted/
  verify_state/verify_upid); PBSReporter collector seam; cross-repo golden + bidirectional
  key-set tests; hub handler parses pbs_snapshots + logs a failed-verify WARN.
- backup: report the ACTUAL vzdump mode (parsed from the task log; PVE may downgrade
  snapshot->stop). proxmox.Storage.Username. config PBSVerifyCadence/secret-dir.
  --selftest=pbs-verify. Backup/restore-to-PBS unchanged.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/hub/report.go

@@ -172,15 +172,15 @@ const (
 // (the bulk-backup mechanism is slice 10). Cross-repo contract: keep byte-identical with
 // felhom.eu/hub and the bidirectional golden key-set test.
 type Backup struct {
-	TargetID         string   `json:"target_id"`         // backup storage name (e.g. "local")
-	VMID             int      `json:"vmid"`              // source guest
-	Archive          string   `json:"archive"`           // produced vzdump volid
-	Mode             string   `json:"mode"`              // snapshot | stop
-	CrashConsistent  bool     `json:"crash_consistent"`  // always true this slice
+	TargetID         string   `json:"target_id"`        // backup storage name (e.g. "local")
+	VMID             int      `json:"vmid"`             // source guest
+	Archive          string   `json:"archive"`          // produced vzdump volid
+	Mode             string   `json:"mode"`             // snapshot | stop
+	CrashConsistent  bool     `json:"crash_consistent"` // always true this slice
 	SizeBytes        int64    `json:"size_bytes"`
 	Success          bool     `json:"success"`
 	Error            string   `json:"error,omitempty"`
-	StartedAt        string   `json:"started_at"`        // RFC3339
+	StartedAt        string   `json:"started_at"` // RFC3339
 	DurationSeconds  float64  `json:"duration_seconds"`
 	UncoveredVolumes []string `json:"uncovered_volumes"` // backup=0/unset mountpoints (bulk gap)
 }
@@ -198,8 +198,26 @@ type RestoreTest struct {
 	DurationSeconds float64 `json:"duration_seconds"`
 }
 
-type PBSSnapshot struct{} // slice 6 Phase B: PBS snapshot inventory fields TBD
-type AuditEntry struct{}  // audit-log tail entry fields TBD
+// PBSSnapshot is one PBS (offsite) snapshot's inventory + integrity state (doc 03 §8, slice
+// 6 Phase B). Sourced from the PBS API (internal/pbs). `verify_state` is the load-bearing
+// field — "none" until a verify runs, then "ok"/"failed" (a failed verify is the loudest
+// offsite-DR signal). `encrypted` is derived from the snapshot's data crypt-mode
+// (zero-knowledge: the PBS server can't read it). Cross-repo contract — byte-identical golden
+// + bidirectional key-set test, the slice-5/6 pattern.
+type PBSSnapshot struct {
+	Namespace   string `json:"namespace"`   // "root" = default ns
+	BackupType  string `json:"backup_type"` // ct | vm
+	BackupID    string `json:"backup_id"`
+	BackupTime  string `json:"backup_time"` // RFC3339
+	SizeBytes   int64  `json:"size_bytes"`
+	Owner       string `json:"owner"`
+	Protected   bool   `json:"protected"`
+	Encrypted   bool   `json:"encrypted"`
+	VerifyState string `json:"verify_state"` // ok | failed | none
+	VerifyUPID  string `json:"verify_upid,omitempty"`
+}
+
+type AuditEntry struct{} // audit-log tail entry fields TBD
 
 // ControlEnvelope is the hub's 200 response to a host-report. This slice the agent
 // adopts ONLY PollIntervalSeconds; the rest are reserved/forward-compat fields it