fix(networking): treat host-network services as host-exposed in summaries (#1430)

The exposure summaries derived a stack's exposure solely from the declared
published-port list, so a service running with network_mode: host (which
publishes every container port on the host but declares no ports:) was
under-reported as less exposed than it actually is.

Capture network_mode in the lightweight dependency parser, add an
isHostNetwork predicate, and treat a host-network service as exposed and
publishing across the Fleet networking summary, the Stack Dossier export, and
the Networking panel, matching how the Compose Doctor already flags host
networking.

backend/src/__tests__/compose-dependency-parse.test.ts

@@ -66,6 +66,15 @@ describe('parseComposeDependencies - ports', () => {
   });
 });
 
+describe('parseComposeDependencies - network_mode', () => {
+  it('captures network_mode and leaves it undefined when absent', () => {
+    const host = parseComposeDependencies(svc('web', 'image: nginx\nnetwork_mode: host'));
+    expect(host.services[0].networkMode).toBe('host');
+    const none = parseComposeDependencies(svc('web', 'image: nginx'));
+    expect(none.services[0].networkMode).toBeUndefined();
+  });
+});
+
 describe('parseComposeDependencies - top-level resources', () => {
   it('normalizes external (bool), legacy external object, and name: override', () => {
     const r = parseComposeDependencies('services:\n  web:\n    image: nginx\nnetworks:\n  a:\n  b:\n    external: true\n  c:\n    external:\n      name: legacy_net\n  d:\n    name: custom_net\nvolumes:\n  v:\n    external: true\n');