Network: consolidate into one tabbed hub; subnet devices span all asset types

Replaces the two flat "Network Devices" + "View Networks" nav entries with a
single "Network" entry opening a tabbed hub: Devices | Networks | VLANs
(NetworkHub renders the existing device list, the subnet browse, and the VLAN
list; VLANs is now reachable outside Settings). /network -> hub; /networks
redirects to the Networks tab; subnet detail stays at /networks/:id.

Subnet "Devices on this network" now matches ANY asset whose primary IP falls in
the CIDR (PCs, printers, machines, measuring tools - not just network devices),
computed on the core Communication + Asset tables; each row links to its typed
detail (extension id resolved lazily/guarded per plugin). Fixes the empty list -
printers and PCs carry IPs and now appear (e.g. 35 devices on 10.80.92.0/24).

Also: subnet-browse search uses the standard form-control styling; dropped the
redundant per-tab page header.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/router/routes/network.js

@@ -5,7 +5,7 @@ export default [
   {
     path: 'network',
     name: 'network',
-    component: () => import('../../views/network/NetworkDevicesList.vue'),
+    component: () => import('../../views/network/NetworkHub.vue'),
     meta: { plugin: 'network' }
   },
   {
@@ -27,10 +27,9 @@ export default [
     meta: { requiresAuth: true, plugin: 'network' }
   },
   {
+    // Legacy path -> the Networks tab of the hub.
     path: 'networks',
-    name: 'networks',
-    component: () => import('../../views/network/SubnetsBrowse.vue'),
-    meta: { plugin: 'network' }
+    redirect: { path: '/network', query: { tab: 'networks' } }
   },
   {
     path: 'networks/:id',