Add "View Networks": front-facing subnet browse + detail with attached devices

Subnets previously lived only under Settings, easily confused with the Network
Devices asset list. Add a front-facing browse + detail:

- Nav: rename "Network" -> "Network Devices"; add "View Networks" (subnets), both
  under Assets (network plugin get_navigation_items; frontend fallback matched).
- /networks (SubnetsBrowse): all subnets with name / CIDR / type / VLAN / notes,
  searchable, row-click to detail.
- /networks/:id (SubnetDetail): the subnet (CIDR, network address, type, VLAN,
  gateway, notes) plus the network devices whose primary IP falls inside its
  CIDR - get_subnet now computes that membership in Python (a device's IP lives
  in a Communication row, so it is not a plain SQL join).

Verified on the import DB: 37 networks list (real WJ subnets), detail renders.

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

frontend/src/views/network/SubnetDetail.vue

@@ -0,0 +1,81 @@
+<template>
+  <div class="detail-page">
+    <div v-if="loading" class="loading">Loading...</div>
+    <div v-else-if="!subnet" class="empty-state"><p>Network not found.</p></div>
+    <template v-else>
+      <div class="page-header">
+        <h1>{{ subnet.name || subnet.cidr }}</h1>
+        <router-link to="/networks" class="btn btn-secondary">Back to Networks</router-link>
+      </div>
+
+      <div class="content-grid">
+        <div class="content-column">
+          <div class="section-card">
+            <h3 class="section-title">Network</h3>
+            <div class="info-list">
+              <div class="info-row"><span class="info-label">CIDR</span><span class="info-value mono">{{ subnet.cidr }}</span></div>
+              <div class="info-row"><span class="info-label">Network Address</span><span class="info-value mono">{{ subnet.networkaddress || '-' }}</span></div>
+              <div class="info-row"><span class="info-label">Type</span><span class="info-value">{{ subnet.subnettype || '-' }}</span></div>
+              <div class="info-row"><span class="info-label">VLAN</span><span class="info-value">{{ subnet.vlannumber || subnet.vlanid || '-' }}</span></div>
+              <div class="info-row" v-if="subnet.gatewayip"><span class="info-label">Gateway</span><span class="info-value mono">{{ subnet.gatewayip }}</span></div>
+            </div>
+          </div>
+
+          <div class="section-card" v-if="subnet.description">
+            <h3 class="section-title">Notes</h3>
+            <div class="notes-content">{{ subnet.description }}</div>
+          </div>
+        </div>
+
+        <div class="content-column">
+          <div class="section-card">
+            <h3 class="section-title">Devices on this network ({{ devices.length }})</h3>
+            <div v-if="devices.length === 0" class="empty-state"><p>No devices found in this range.</p></div>
+            <div v-else class="table-container">
+              <table>
+                <thead>
+                  <tr><th>Device</th><th>IP</th><th>Type</th></tr>
+                </thead>
+                <tbody>
+                  <tr v-for="dev in devices" :key="dev.networkdeviceid">
+                    <td>
+                      <router-link :to="`/network/${dev.networkdeviceid}`">
+                        {{ dev.name || dev.hostname || dev.assetnumber }}
+                      </router-link>
+                    </td>
+                    <td class="mono">{{ dev.ipaddress }}</td>
+                    <td>{{ dev.networkdevicetypename || '-' }}</td>
+                  </tr>
+                </tbody>
+              </table>
+            </div>
+          </div>
+        </div>
+      </div>
+    </template>
+  </div>
+</template>
+
+<script setup>
+import { ref, computed, onMounted } from 'vue'
+import { useRoute } from 'vue-router'
+import { networkApi } from '@/api'
+
+const route = useRoute()
+const subnet = ref(null)
+const loading = ref(true)
+
+const devices = computed(() => subnet.value?.devices || [])
+
+async function load() {
+  loading.value = true
+  try {
+    const response = await networkApi.subnets.get(route.params.id)
+    subnet.value = response.data?.data || response.data
+  } finally {
+    loading.value = false
+  }
+}
+
+onMounted(load)
+</script>