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/SubnetsBrowse.vue

@@ -0,0 +1,79 @@
+<template>
+  <div>
+    <div class="page-header">
+      <h1>Networks</h1>
+    </div>
+
+    <div class="filters">
+      <input v-model="search" type="text" placeholder="Search networks..." class="search-input" />
+    </div>
+
+    <div class="card">
+      <div v-if="loading" class="loading">Loading...</div>
+      <div v-else-if="filtered.length === 0" class="empty-state"><p>No networks found.</p></div>
+      <div v-else class="table-container">
+        <table>
+          <thead>
+            <tr>
+              <th>Name</th>
+              <th>CIDR</th>
+              <th>Type</th>
+              <th>VLAN</th>
+              <th>Notes</th>
+              <th class="actions"></th>
+            </tr>
+          </thead>
+          <tbody>
+            <tr v-for="subnet in filtered" :key="subnet.subnetid" class="clickable-row"
+                @click="$router.push(`/networks/${subnet.subnetid}`)">
+              <td>{{ subnet.name || '-' }}</td>
+              <td class="mono">{{ subnet.cidr }}</td>
+              <td>{{ subnet.subnettype || '-' }}</td>
+              <td>{{ subnet.vlannumber || subnet.vlanid || '-' }}</td>
+              <td class="cell-truncate" :title="subnet.description">{{ subnet.description || '-' }}</td>
+              <td class="actions">
+                <router-link :to="`/networks/${subnet.subnetid}`" class="btn btn-sm btn-secondary" @click.stop>View</router-link>
+              </td>
+            </tr>
+          </tbody>
+        </table>
+      </div>
+    </div>
+  </div>
+</template>
+
+<script setup>
+import { ref, computed, onMounted } from 'vue'
+import { networkApi } from '@/api'
+
+const subnets = ref([])
+const loading = ref(true)
+const search = ref('')
+
+const filtered = computed(() => {
+  const term = search.value.trim().toLowerCase()
+  if (!term) return subnets.value
+  return subnets.value.filter(s =>
+    (s.name || '').toLowerCase().includes(term) ||
+    (s.cidr || '').toLowerCase().includes(term) ||
+    (s.subnettype || '').toLowerCase().includes(term) ||
+    (s.description || '').toLowerCase().includes(term))
+})
+
+async function load() {
+  loading.value = true
+  try {
+    const response = await networkApi.subnets.list({ per_page: 1000 })
+    subnets.value = response.data?.data || response.data || []
+  } finally {
+    loading.value = false
+  }
+}
+
+onMounted(load)
+</script>
+
+<style scoped>
+.clickable-row { cursor: pointer; }
+.clickable-row:hover { background: var(--bg); }
+</style>