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>

plugins/network/plugin.py

@@ -208,17 +208,11 @@ class NetworkPlugin(BasePlugin):
         """Return navigation menu items."""
         return [
             {
-                'name': 'Network Devices',
+                'name': 'Network',
                 'icon': 'network-wired',
                 'route': '/network',
                 'position': 18,
             },
-            {
-                'name': 'View Networks',
-                'icon': 'globe',
-                'route': '/networks',
-                'position': 19,
-            },
         ]
 
     def get_permissions(self) -> List: