varaverk: monitor overhaul — CPU/memory/network/streams cards; scheduler polish

Monitor tab:
- CPU card: per-core bars (freq-colored), overall usage bar, rolling history chart
- Memory card: breakdown by system/VM/ZFS/Docker/free with progress bars
- Network card: LAN + ext + Tailscale IP display, live RX/TX chart with auto-scale
- Streams card: Emby/Jellyfin/Plex sessions with playback bar and server badges
- GPU card: adds power draw, encode%, decode% meters
- Transcode card: ramdisk vs SSD location pill, session count, flip history
- Canvas chart helpers: vvDrawChart, vvDrawNetChart, vvMeter, vvFmtBps, vvFmtGib

api/monitor.php: adds cpu, mem, net to response payload

Plugin/usr/local/emhttp/plugins/varaverk/api/monitor.php

@@ -5,6 +5,9 @@ require_once dirname(__DIR__) . '/include/monitor.php';
 echo json_encode([
     'fallback'    => vv_fallback_state(),
     'resources'   => vv_system_resources(),
+    'cpu'         => vv_cpu_per_core(),
+    'mem'         => vv_memory_breakdown(),
+    'net'         => vv_network_stats(),
     'gpu'         => vv_gpu_stats(),
     'gpu_procs'   => vv_gpu_processes(),
     'containers'  => vv_docker_containers(),