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>

CLAUDE.md

@@ -15,7 +15,7 @@
 - Module `gitea.dooplex.hu/admin/felhom-agent`; binary `felhom-agent` (`cmd/felhom-agent/`).
 - **Pure Go stdlib + `golang.org/x/crypto` only** — no web frameworks.
 - `go.mod` directive **go 1.25.0**; dep `golang.org/x/crypto v0.52.0` (declares go 1.25, will NOT build on Go 1.24). The **build server (192.168.0.180) runs go1.26.0** (upstream Go on PATH, backward-compatible). Build/run the agent there for live tests (same LAN as the demo host).
-- Version: `version` var in `cmd/felhom-agent/main.go`, overridable via `-ldflags "-X main.version=<v>"`; `--version` flag. **Current: v0.6.0-rc1** (slice 6 Phase A: backup + the self-restore-test, local target; PBS = Phase B). Bump on meaningful changes + add a CHANGELOG entry.
+- Version: `version` var in `cmd/felhom-agent/main.go`, overridable via `-ldflags "-X main.version=<v>"`; `--version` flag. **Current: v0.6.0** (slice 6 complete: backup + self-restore-test + the PBS offsite tier — verify + PBS-API client + PBSSnapshot reporting). Bump on meaningful changes + add a CHANGELOG entry.
 
 ## Layout
 
@@ -29,6 +29,7 @@ internal/hub/        daemon: HostReport collector + Bearer client + resilient Lo
 internal/reconcile/  reconcile engine + reversibility gate + op journal + crash recovery + restore-test
 internal/storage/    storage-target observer + durable_id + fast-poll watchdog (slice 5)
 internal/backup/     vzdump backup runner + restore-test scheduler + report store (slice 6)
+internal/pbs/        PBS-API client (fingerprint-pinned) + verify maintenance loop (slice 6 Phase B)
 ```
 
 ## Proxmox model (the load-bearing rules)
@@ -56,7 +57,8 @@ Built in slices, all on `main`:
 - **v0.5.0-rc1** — slice-5 **Phase A** (read-only, live): `internal/storage` — the `StorageTarget` wire contract (filled the slice-3 stub), `durable_id` derivation per type, the `Observer`, and the **storage watchdog** (third daemon goroutine; fast-poll → debounced out-of-band report on a known target's attach/disconnect). Hub ingest accepts/persists `storage_targets`; cross-repo golden byte-identical.
 - **v0.5.0** — slice-5 **Phase B** (the host-root surface): the `HostOps` seam + `SudoHostOps` (systemd `.mount` units by fs-UUID, detach, SMART, lvs) behind a **strict argument validator** (the adversarial matrix is the headline security test — hostile UUID/path/device refused with zero exec); SMART (SATA+NVMe) + thin-pool metadata enrichment; the watchdog's benign **re-mount response** (off the poll path); the **disk-grow executor** (`pct resize`, grow-only, benign) and **destructive storage ops** through the slice-4 gate (target-scoped; built + tested, inert live); `--selftest=storage [-watch]`; `configs/felhom-agent.sudoers`.
 - **v0.6.0-rc1** — slice-6 **Phase A** (backup + self-restore-test, local target): proxmox `DestroyLXC`/`Vzdump`-notes/`LatestBackupVolID`; `Engine.RunRestoreTest` (journaled scratch lifecycle: restore-to-new → net link-down → boot → verify running → defer teardown, all benign); `Recover` extended to reap a leaked scratch guest (Scratch journal flag, special-cased before the UPID path); `internal/backup` (runner + bulk-gap + cadence scheduler + report store); hub `Backup`/`RestoreTest` filled (cross-repo golden + hub logs a failed restore-test); `--selftest=backup`/`--selftest=restore-test`. Live-validated on demo-felhom.
-- **Next: slice 6 Phase B (PBS)** — datastore on the USB, zero-knowledge key custody, restore-from-PBS, PBS integrity-verify (the lighter frequent check). Then slice 7 (provisioning + identity-reset + golden base, §9).
+- **v0.6.0** — slice-6 **Phase B** (PBS offsite tier): `internal/pbs` — a fingerprint-pinned, token-authed PBS-API client (Verify/Snapshots/TaskStatus, node-from-UPID); the verify maintenance loop (own cadence, NOT gated/journaled — like the watchdog); `PBSSnapshot` reporting filled (cross-repo golden + hub failed-verify WARN); truthful vzdump mode from the task log; `--selftest=pbs-verify`. Backup/restore-to-PBS reuse Phase A unchanged. Live-validated against the spike's DooPlex PBS.
+- **Next: slice 7 (provisioning + identity-reset + golden base, §9)** — the unified bring-up primitive; restore-overwrite + decommission executors the gate already guards; escrow + host-loss DR.
 
 ## Demo host (for live tests)