feat(fleet): add read-only dependency map tab (#1324)

* feat(fleet): add read-only dependency map tab

Add a fleet-wide Dependencies tab to Fleet view that maps how stacks,
services, networks, volumes, and ports relate, with flags for missing
dependencies, port conflicts, orphaned resources, and cross-stack shared
resources. Read-only; filterable by stack, node, and flag; collapsed by
default with a list-view fallback at scale.

The graph is derived at request time from Docker and compose metadata, so
no new table or persisted state is introduced. A per-node graph endpoint
feeds a hub aggregation endpoint that fans out across the fleet and
degrades gracefully, surfacing unreachable or unparseable nodes inline
while the rest of the map still renders.

* fix(fleet): harden dependency map flag detection and remote merge

Address review findings on the dependency map:
- Port-conflict detection now does pairwise host-scope overlap, so an
  unrelated bind on the same port and protocol but a different specific host
  IP is no longer flagged, and the flag lands on the exact scoped port node.
- A running service's depends_on target is only considered satisfied when it
  is actually running, so a crashed (exited) dependency is surfaced while a
  deliberately stopped stack stays quiet.
- Declared external networks and volumes are reported missing when they do
  not exist on the host instead of being assumed present.
- The hub deep-validates each remote node-graph payload before merging, so a
  reachable-but-malformed remote degrades to a single node error rather than
  failing the whole fleet map, and the validation failure is logged.
- Searching or filtering on a network, volume, or port now also reveals the
  services that claim it and their stacks.

frontend/src/components/FleetView.tsx

@@ -1,7 +1,7 @@
 import {
     RefreshCw, Search, Camera, Plus,
     Network, SlidersHorizontal,
-    Send, KeyRound, ArrowLeftRight, Wrench,
+    Send, KeyRound, ArrowLeftRight, Wrench, Workflow,
 } from 'lucide-react';
 import { FleetMasthead } from './fleet/FleetMasthead';
 import { ReconnectingOverlay } from './FleetView/ReconnectingOverlay';
@@ -26,6 +26,7 @@ import { FederationTab } from './fleet/FederationTab';
 import { DeploymentsTab } from './blueprints/DeploymentsTab';
 import { FleetActionsTab } from './fleet/FleetActions/FleetActionsTab';
 import { SecretsTab } from './fleet/secrets/SecretsTab';
+import { DependencyMapTab } from './fleet/DependencyMapTab';
 import { useNodeActions } from './nodes/useNodeActions';
 import { SettingsPrimaryButton } from './settings/SettingsActions';
 
@@ -89,6 +90,11 @@ export function FleetView({ onNavigateToNode }: FleetViewProps) {
                                     <SlidersHorizontal className="w-4 h-4 mr-1.5" />Status
                                 </TabsTrigger>
                             </TabsHighlightItem>
+                            <TabsHighlightItem value="dependencies">
+                                <TabsTrigger value="dependencies">
+                                    <Workflow className="w-4 h-4 mr-1.5" />Dependencies
+                                </TabsTrigger>
+                            </TabsHighlightItem>
                             <span aria-hidden className="self-center mx-1 h-4 w-px bg-border" />
                             {isPaid && (
                                 <TabsHighlightItem value="deployments">
@@ -201,6 +207,9 @@ export function FleetView({ onNavigateToNode }: FleetViewProps) {
                 <TabsContent value="configuration">
                     <FleetConfiguration />
                 </TabsContent>
+                <TabsContent value="dependencies">
+                    <DependencyMapTab />
+                </TabsContent>
                 {isPaid && (
                     <TabsContent value="deployments">
                         <DeploymentsTab />