feat(escrow): v0.138.0 — "awaiting hub confirmation" waiting state

After a completed escrow ceremony the Távoli mentés page showed the yellow
"Helyreállítási kód szükséges" card for ~15 min until the next hub-report ACK
flipped pending→escrowed. Phase-0 diagnosis (read-only) = verdict A (report-cycle
lag), already resolved on the demo box (escrow_state:"escrowed"); hub Hypothesis B
verified false (SaveHostEscrow ON CONFLICT already clears stale_at on upload) → no
hub change.

- settings.OffboxTarget.CeremonyCompletedAt: stamped on the recovery-code claim,
  zeroed on the auto-confirmer Flip + the deprecated manual confirm; persisted.
- web/handlers.go: offboxCeremonyWaitState + escrowCeremonyGraceWindow (35m).
- backups_remote.html: info "megerősítésre vár, legfeljebb 15 perc" card → warn
  "a megerősítés nem érkezett meg" past the window. Existing branches untouched.
- backups_escrow.html: "Mi történik ezután?" note on the wizard's final step.
- Test web/escrow_wait_state_test.go (truth table + red-proof recorded in REPORT).

No scheduler/agent/hub/endpoint changes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017qDiBqKKQ5vPB5fXBqu7Kp

controller/README.md

@@ -882,6 +882,15 @@ not just those with HDD data. Non-HDD apps can configure destination, method, an
 >   staged secret) sets an in-memory stale flag (`EscrowAutoConfirmer.StaleBlob` → the Távoli
 >   mentés card's warning + re-ceremony CTA) + one warn per distinct hub hash. State never flips,
 >   runs never block; a covering blob (or a fresh auto-confirm) clears it.
+>   **Awaiting-confirmation card (v0.138.0):** the flip above lands on the *next* report ACK, so a
+>   just-finished ceremony sits pending for up to ~15 min. To avoid re-showing the yellow
+>   "Helyreállítási kód szükséges" card during that gap, a successful recovery-code **claim** stamps
+>   `OffboxTarget.CeremonyCompletedAt` (RFC3339, persisted; zeroed on the flip). While stamped and
+>   pending, `/backups/remote` shows an **info** "megerősítésre vár, legfeljebb 15 perc" card
+>   (`offboxCeremonyWaitState`); past `escrowCeremonyGraceWindow` (35 min = 2 cycles + slack) it
+>   degrades to a **warn** "a megerősítés nem érkezett meg" + re-ceremony CTA — never an indefinite
+>   wait. The wizard's final step shows a matching "Mi történik ezután?" note. Display-only: no state
+>   change, no run-gate effect. (Phase-0 A: the wait itself is correct; only the feedback was missing.)
 > - **Injection guard** (`ValidateOffboxTarget`): host/user/repo must not start with `-` (ssh
 >   option-injection) or carry metacharacters/traversal; `OffboxConfigured` fails closed on an invalid
 >   target. Image: `restic` + `openssh-client` (re-added; restic's sftp backend shells out to `ssh`).