feat(i18n): pluralize sidebar network/device counters

Show singular form when count is 1 (Network, Device, Réseau, Équip., Red, Equipo)
across all three supported languages (fr, en, es).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/App.vue

@@ -42,11 +42,11 @@
         <div class="stats">
           <div class="stat">
             <span class="stat-val">{{ vlans.length }}</span>
-            <span class="stat-lbl">{{ t('statsNetworks') }}</span>
+            <span class="stat-lbl">{{ vlans.length === 1 ? t('statsNetwork') : t('statsNetworks') }}</span>
           </div>
           <div class="stat">
             <span class="stat-val">{{ devices.length }}</span>
-            <span class="stat-lbl">{{ t('statsDevices') }}</span>
+            <span class="stat-lbl">{{ devices.length === 1 ? t('statsDevice') : t('statsDevices') }}</span>
           </div>
         </div>
         <button class="btn-export" @click="exportJson">{{ t('exportJson') }}</button>

frontend/src/i18n.js

@@ -14,7 +14,9 @@ const LANGS = {
     tabNetworks: 'Réseaux',
     tabDevices: 'Équipements',
     discovery: '🔍 Découverte auto',
+    statsNetwork: 'Réseau',
     statsNetworks: 'Réseaux',
+    statsDevice: 'Équip.',
     statsDevices: 'Équip.',
     exportJson: '⬇ Export JSON',
     importJson: '⬆ Import JSON',
@@ -170,7 +172,9 @@ const LANGS = {
     tabNetworks: 'Networks',
     tabDevices: 'Devices',
     discovery: '🔍 Auto discovery',
+    statsNetwork: 'Network',
     statsNetworks: 'Networks',
+    statsDevice: 'Device',
     statsDevices: 'Devices',
     exportJson: '⬇ Export JSON',
     importJson: '⬆ Import JSON',
@@ -320,7 +324,9 @@ const LANGS = {
     tabNetworks: 'Redes',
     tabDevices: 'Equipos',
     discovery: '🔍 Descubrimiento auto',
+    statsNetwork: 'Red',
     statsNetworks: 'Redes',
+    statsDevice: 'Equipo',
     statsDevices: 'Equipos',
     exportJson: '⬇ Exportar JSON',
     importJson: '⬆ Importar JSON',