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.

frontend/src/components/FleetView.tsx

@@ -34,11 +34,10 @@ export function FleetView({ onNavigateToNode }: FleetViewProps) {
     const experimental = useExperimental();
 
     const { prefs, updatePrefs } = useFleetPreferences();
-    const updateStatus = useFleetUpdateStatus({ isPaid });
+    const updateStatus = useFleetUpdateStatus();
     const overview = useFleetOverview({ isPaid, prefs, updatePrefs, updateStatuses: updateStatus.updateStatuses });
 
     useFleetPolling({
-        isPaid,
         fetchOverview: overview.fetchOverview,
         fetchUpdateStatus: updateStatus.fetchUpdateStatus,
         updateStatuses: updateStatus.updateStatuses,
@@ -69,13 +68,11 @@ export function FleetView({ onNavigateToNode }: FleetViewProps) {
                             <TabsHighlightItem value="overview">
                                 <TabsTrigger value="overview">Overview</TabsTrigger>
                             </TabsHighlightItem>
-                            {isPaid && (
-                                <TabsHighlightItem value="snapshots">
-                                    <TabsTrigger value="snapshots">
-                                        <Camera className="w-4 h-4 mr-1.5" />Snapshots
-                                    </TabsTrigger>
-                                </TabsHighlightItem>
-                            )}
+                            <TabsHighlightItem value="snapshots">
+                                <TabsTrigger value="snapshots">
+                                    <Camera className="w-4 h-4 mr-1.5" />Snapshots
+                                </TabsTrigger>
+                            </TabsHighlightItem>
                             {isAdmiral && experimental && (
                                 <TabsHighlightItem value="routing">
                                     <TabsTrigger value="routing">
@@ -114,17 +111,15 @@ export function FleetView({ onNavigateToNode }: FleetViewProps) {
                         </TabsHighlight>
                     </TabsList>
                     <div className="flex items-center gap-2">
-                        {isPaid && (
-                            <Button
-                                variant="outline"
-                                size="sm"
-                                onClick={updateStatus.checkUpdates}
-                                className="gap-2"
-                            >
-                                <Search className="w-4 h-4" />
-                                Check Updates
-                            </Button>
-                        )}
+                        <Button
+                            variant="outline"
+                            size="sm"
+                            onClick={updateStatus.checkUpdates}
+                            className="gap-2"
+                        >
+                            <Search className="w-4 h-4" />
+                            Check Updates
+                        </Button>
                         <Button
                             variant="outline"
                             size="sm"
@@ -155,22 +150,19 @@ export function FleetView({ onNavigateToNode }: FleetViewProps) {
                         labelFilters={overview.labelFilters}
                         onLabelFiltersChange={overview.setLabelFilters}
                         onClearFilters={overview.clearFilters}
-                        isPaid={isPaid}
                         fleetStackLabelMap={overview.fleetStackLabelMap}
                         updateStatusMap={overview.updateStatusMap}
                         onNavigateToNode={onNavigateToNode}
-                        onUpdate={isPaid ? updateStatus.triggerNodeUpdate : undefined}
+                        onUpdate={updateStatus.triggerNodeUpdate}
                         updatingNodeId={updateStatus.updatingNodeId}
-                        onRetryUpdate={isPaid ? updateStatus.retryNodeUpdate : undefined}
-                        onDismissUpdate={isPaid ? updateStatus.dismissNodeUpdate : undefined}
+                        onRetryUpdate={updateStatus.retryNodeUpdate}
+                        onDismissUpdate={updateStatus.dismissNodeUpdate}
                     />
                 </TabsContent>
 
-                {isPaid && (
-                    <TabsContent value="snapshots">
-                        <FleetSnapshots />
-                    </TabsContent>
-                )}
+                <TabsContent value="snapshots">
+                    <FleetSnapshots />
+                </TabsContent>
                 {isAdmiral && experimental && (
                     <TabsContent value="routing">
                         <AdmiralGate>
@@ -233,6 +225,7 @@ export function FleetView({ onNavigateToNode }: FleetViewProps) {
                 retryNodeUpdate={updateStatus.retryNodeUpdate}
                 dismissNodeUpdate={updateStatus.dismissNodeUpdate}
                 triggerUpdateAll={updateStatus.triggerUpdateAll}
+                canBulkUpdate={isPaid}
             />
 
             <LocalUpdateConfirmDialog