feat(snapshots): preserve stack dossiers with fleet snapshots (#1339)

* feat(snapshots): preserve stack dossiers with fleet snapshots

Fleet snapshots can now optionally capture each stack's Dossier notes
alongside its compose and .env files, so a recovery restores the
operational knowledge around a stack, not just its configuration.

- Opt-in global setting "snapshot_documentation" (default off), toggled
  from the renamed Fleet settings section.
- Capture reads local dossiers from the database and remote dossiers over
  the Distributed API proxy; only stacks with notes are recorded, and
  secret values are never included.
- Captured notes are stored encrypted at rest in a new fleet_snapshots
  column and surfaced in the snapshot detail view behind a badge.
- Cloud and downloaded archives gain a documentation.json (archive_version 2).
- Restore stays conservative: dossier notes are written back only when the
  operator explicitly opts in, on both single-stack and restore-all paths.
- Existing snapshots and archives remain valid; behavior is unchanged when
  the setting is off.

* fix(snapshots): harden dossier-notes restore against bad input and partial failures

Address review findings on the documentation-snapshots restore path:

- Parse `restoreNotes` strictly (=== true) on single-stack restore, matching
  restore-all, so a stray non-boolean can never opt in to overwriting notes.
- Guard findSnapshotDossier: require an array of stacks and real dossier
  content, so a malformed or all-blank entry can't clobber current notes.
- Make the dossier-notes write non-fatal relative to the file restore: a notes
  failure (e.g. a remote dossier PUT) is caught, reported via `notesError`, and
  no longer 500s the single restore or fails the stack in restore-all once the
  files are already written.
- Surface the partial outcome in the UI: a warning toast on single restore, a
  summary note on restore-all, and gate the "Documentation captured" badge and
  restore-all notes control on captured stacks while rendering capture warnings.

Adds tests for strict parsing, malformed/blank blobs, remote notes restore
(success + non-fatal failure, single and bulk), and scheduled capture-on.

* fix(snapshots): drop unused binding in restore-all remote notes test

The restore-all remote notes test destructured a node id it never uses
(restore-all is driven by snapshot id alone), tripping no-unused-vars and
failing the lint step. Bind only the snapshot id.

frontend/src/components/settings/registry.ts

@@ -126,9 +126,9 @@ export const SETTINGS_ITEMS: readonly SettingsItemMeta[] = [
     {
         id: 'fleet-mesh',
         group: 'infrastructure',
-        label: 'Fleet Mesh',
-        description: 'Data-plane network behavior for the cross-node service mesh.',
-        keywords: ['mesh', 'network', 'recreate', 'fleet', 'routing', 'data plane', 'sencho_mesh'],
+        label: 'Fleet',
+        description: 'Cross-node service-mesh data plane and fleet-snapshot documentation capture.',
+        keywords: ['mesh', 'network', 'recreate', 'fleet', 'routing', 'data plane', 'sencho_mesh', 'snapshot', 'documentation', 'dossier'],
         tier: null,
         scope: 'node',
         adminOnly: true,