feat: scheduled backups, availability tracking, PoE power metrics (v0.11.2 Beta)

P1 — Scheduled Backups
- BackupService.createBackup() now accepts a `type` param (manual/scheduled)
- PollerService: cronMatchesNow() parser + runScheduledBackups() + Redis 1h gate
- Settings page: backup schedule toggle + cron expression input with examples

P2 — Uptime/Availability Tracking
- DB: device_availability table (went_offline_at, came_back_online_at, duration_seconds)
- PollerService: inserts outage rows on offline detection, closes them on recovery
- GET /api/metrics/device/:id/availability?range=30d endpoint
- /api/metrics/summary now includes fleet 30-day uptime %
- DeviceDetailPage: 30-day availability card (uptime %, outage count, longest outage)
- DashboardPage HealthBar: Uptime 30d mini-stat

P3 — PoE Power Draw Metrics
- DeviceCollector.collectPoePower() queries /interface/ethernet/poe/monitor for switches
- Writes poe_power measurement to InfluxDB (tags: device_id, port; fields: watts, current_ma, voltage_v)
- GET /api/metrics/device/:id/poe endpoint (current per-port + 1h history)
- SwitchPortDiagram: amber watt badge on PoE-active ports
- HardwareTab: PoE budget section showing active ports and total watts

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

backend/src/services/mikrotik/DeviceCollector.ts

@@ -71,6 +71,9 @@ export class DeviceCollector {
     if (this.device.device_type === 'wireless_ap') {
       await this.collectWirelessStats();
     }
+    if (this.device.device_type === 'switch') {
+      await this.collectPoePower();
+    }
     await this.updateDeviceStatus('online');
   }
 
@@ -1727,6 +1730,37 @@ export class DeviceCollector {
     return this.client.execute('/interface/ethernet/poe/print', { detail: '' }).catch(() => []);
   }
 
+  async collectPoePower(): Promise<void> {
+    try {
+      const ports = await this.client
+        .execute('/interface/ethernet/poe/monitor', { once: '' })
+        .catch(() => [] as Record<string, string>[]);
+      if (ports.length === 0) return;
+
+      const writeApi = getWriteApi();
+      for (const port of ports) {
+        const name = port['name'] || port['port-name'] || '';
+        if (!name) continue;
+        const watts = parseFloat(port['poe-out-voltage'] || '0') * parseFloat(port['poe-out-current'] || '0') / 1000;
+        const currentMa = parseFloat(port['poe-out-current'] || '0');
+        const voltageV = parseFloat(port['poe-out-voltage'] || '0');
+        writeApi.writePoint(
+          new Point('poe_power')
+            .tag('device_id', String(this.device.id))
+            .tag('device_name', this.device.name)
+            .tag('port', name)
+            .floatField('watts', parseFloat(watts.toFixed(2)))
+            .floatField('current_ma', currentMa)
+            .floatField('voltage_v', voltageV)
+            .timestamp(new Date())
+        );
+      }
+      await writeApi.flush().catch((e) => console.error('InfluxDB PoE flush error:', e));
+    } catch (err) {
+      console.error(`[${this.device.name}] Failed to collect PoE power:`, err);
+    }
+  }
+
   // ─── Port VLAN config ─────────────────────────────────────────────────────
 
   async setPortVlanConfig(