Sync with the server and scan-to-join onboarding

- Device key (DeviceSigner): Windows TPM via CNG with a DPAPI-sealed software
  fallback, Linux Secret Service with a 0600 file fallback (warned in Settings),
  macOS keychain for dev runs. The store used is recorded; no silent switching.
- SyncService (Tauri-free): server URL and pins, create account with the
  server's setup code, sync after unlock/save/browser save, every 15 min while
  unlocked and on demand, status events, integrity alarm, device list with
  fingerprint approval and revoke.
- Onboarding: "Use my phone" (join_start/poll, QR rendered locally, 6-digit
  code), Emergency Kit from PDF/PNG/JPEG (hayro + rqrr), paste setup code, new
  account. Then only the master password.
- From a signed-in desktop: "Add a phone or tablet" QR with countdown (cancel,
  lock and quit revoke the ticket) and "Approve a computer" via pasted join code.
- KESTROVE_DATA_DIR / KESTROVE_DEVICE_NAME for a second instance; ignored
  live test drives three instances against a real server.
- deny: ignore three unmaintained notices for zbus 5 sub-crates (Linux keyring).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src-tauri/deny.toml

@@ -9,6 +9,11 @@ ignore = [
   { id = "RUSTSEC-2025-0141", reason = "bincode 1.x via uniffi_macros 0.28 (build-time)" },
   { id = "RUSTSEC-2024-0436", reason = "paste via uniffi 0.28 (proc-macro)" },
   { id = "RUSTSEC-2024-0370", reason = "proc-macro-error via glib-macros 0.18 / Tauri gtk stack (proc-macro)" },
+  # zbus 5 sub-crates folded into zbus 6 (no vulnerability). Linux only: keyring's Secret Service store
+  # (device key) still uses zbus 5; revisit when secret-service moves to zbus 6.
+  { id = "RUSTSEC-2026-0370", reason = "zvariant via zbus 5 (keyring Secret Service store, Linux)" },
+  { id = "RUSTSEC-2026-0371", reason = "zbus_names via zbus 5 (keyring Secret Service store, Linux)" },
+  { id = "RUSTSEC-2026-0372", reason = "zvariant_derive via zbus 5 (keyring Secret Service store, Linux)" },
 ]
 
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