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/views/AppLayout.vue

@@ -156,8 +156,7 @@ const defaultNav = [
   { name: 'Map', icon: 'map', route: '/map', position: 4 },
   { name: 'Machines', icon: 'cog', route: '/machines', position: 10 },
   { name: 'PCs', icon: 'desktop', route: '/pcs', position: 15 },
-  { name: 'Network Devices', icon: 'network-wired', route: '/network', position: 18 },
-  { name: 'View Networks', icon: 'globe', route: '/networks', position: 19 },
+  { name: 'Network', icon: 'network-wired', route: '/network', position: 18 },
   { name: 'Printers', icon: 'printer', route: '/printers', position: 20 },
   { name: 'USB Devices', icon: 'usb', route: '/usb', position: 45 },
   { name: 'Applications', icon: 'app-window', route: '/applications', position: 30, section: 'information' },