feat: open security basics, manual fleet ops, and basic fleet management to Community (#930)

Realign tier guards to the user-stated philosophy: Community covers
deploy/monitor at scale plus security basics, Skipper adds automation
and advanced fleet management, Admiral keeps enterprise control.

Community now includes:
- Trivy install / uninstall / update from the Settings Hub (admin role)
- CVE suppressions CRUD (admin role; replicates fleet-wide)
- Manual image scan with vuln, secret, and misconfig results
- Stack-config scan, scan comparison
- Manual fleet snapshots: create, list, view, restore, delete
- Per-node Sencho self-update (Check Updates + per-node Update)
- Fleet Overview search, sort, filters, node-card expand, auto-refresh

Stays paid:
- Scan policies with block_on_deploy enforcement (Skipper+)
- SBOM (SPDX, CycloneDX), SARIF export (Skipper+)
- Bulk Update All across the fleet (Skipper+)
- Scheduled snapshot create (now Skipper, was Admiral)
- Trivy auto-update toggle, fleet-wide policy push (Admiral)

The Settings -> Security tab is unhidden by setting the registry tier to
null. The SecuritySection no longer early-returns a PaidGate; the policy
list, Add Policy button, and policy dialogs are wrapped in {isPaid && }.
The Fleet view drops isPaid gates on the Snapshots tab, Check Updates
button, per-node update handlers, OverviewToolbar grid controls, the
NodeCard expand affordance, and the auto-refresh notice. The
NodeUpdatesSheet receives a canBulkUpdate prop and gates the Update All
button on it. useFleetUpdateStatus and useFleetPolling drop their isPaid
guards so polling runs for Community; useFleetOverview drops the isPaid
wrap on the filter and sort path.

Backend route guards are flipped per the matrix above. The scheduler
tick and requireScheduledTaskTier add 'snapshot' to the Skipper+ branch.
Backend test assertions are inverted for the now-Community endpoints
and a positive Skipper-snapshot-task test is added.

Documentation across features/, api-reference/, and operations/ is
updated to reflect the new tier mapping.

docs/features/licensing.mdx

@@ -23,14 +23,19 @@ Lifetime pricing is an early-adopter offer available for a limited time only.
 
 **Community** includes:
 - Unlimited nodes, compose editor, global logs, app store, alerts, and more
+- Fleet View with search, sort, filters, node-card expand, and topology
+- Manual fleet snapshots (create, browse, restore, delete)
+- Per-node Sencho updates and the Check Updates view
+- Vulnerability scanning: install/update/uninstall Trivy, on-demand scans (vulnerabilities, secrets, misconfigurations), scan comparison, and CVE suppressions
 - Two-factor authentication (TOTP)
 - Custom OIDC single sign-on (works with Authelia, Keycloak, Authentik, Zitadel, Pocket ID, or any spec-compliant OIDC identity provider)
 
 **Skipper** includes everything in Community, plus:
-- Fleet View with drill-down
 - Webhooks and stack labels
-- Atomic deployments and fleet-wide backups
-- Auto-update policies
+- Atomic deployments
+- Bulk **Update All** across the fleet, scheduled scans, scheduled updates, and scheduled fleet snapshots
+- Scan policies with `block_on_deploy` enforcement, SBOM (SPDX, CycloneDX), and SARIF export
+- Auto-update policies for stack images
 - One-click Google, GitHub, and Okta SSO presets
 
 **Admiral** includes everything in Skipper, plus:
@@ -40,7 +45,8 @@ Lifetime pricing is an early-adopter offer available for a limited time only.
 - Audit log and host console
 - API tokens and private registries
 - Notification routing
-- Scheduled operations
+- Auto-update of the managed Trivy binary
+- All other scheduled operations (restart, prune, etc.)
 
 <Tip>
   **SSO is available on every tier.** Community users can integrate any OIDC-compliant identity provider through the Custom OIDC option. Paid tiers add turnkey presets (Google, GitHub, Okta) and LDAP / Active Directory.