feat(wireless+ports): RF Health panels + physical per-port clients (v0.16.1-beta)

Wireless RF Health (fleet Wireless page + per-AP Radios tab):
- Channel usage map across 2.4/5/6 GHz with co-channel overlap; operating
  channel resolved live from /interface/wifi/monitor on the wifi package
  (auto-channel radios report no frequency in /print).
- AP deployment density: client RSSI distribution on the -90..-30 dBm scale
  with a coverage-gap warning.
- AP radio TX retries histogram (0%->35%+) with band selector, derived from
  per-client CCQ (new wireless_radio_quality InfluxDB series).
- WiFi connectivity success funnel (Association/Auth/DHCP) derived from logs.

Per-port connected clients (Ports tab):
- New card lists clients physically connected to a selected port (host/MAC/
  IP/VLAN/connection time, linked to client pages).
- Distinguishes physical clients from the raw MAC table: uplink/trunk ports
  are auto-detected (topology neighbor, multi-VLAN MAC spread, or high MAC
  count) and show an uplink explainer + "view MAC table" disclosure instead
  of every reachable MAC.
- Added clients.first_seen ("connected since"); set once, preserved across polls.

frontend/src/utils/wifiChannels.ts

@@ -0,0 +1,100 @@
+// WiFi channel helpers for the RF Health panels.
+//
+// Maps RouterOS radio frequencies (MHz) to a band + channel number, supplies the
+// canonical channel lists each band's channel map renders, and provides the
+// bucketing used by the TX-retries histogram and the RSSI density scale.
+
+export type RfBand = '2.4' | '5' | '6';
+
+// Canonical channel scales shown on the channel map (mirrors what UniFi displays).
+export const CHANNELS_24: number[] = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11];
+export const CHANNELS_5: number[] = [
+  36, 40, 44, 48, 52, 56, 60, 64, 100, 104, 108, 112, 116, 120, 124, 128,
+  132, 136, 140, 144, 149, 153, 157, 161, 165,
+];
+// 6 GHz: channels 1..233 in steps of 4
+export const CHANNELS_6: number[] = Array.from({ length: 59 }, (_, i) => 1 + i * 4);
+
+export const BAND_CHANNELS: Record<RfBand, number[]> = {
+  '2.4': CHANNELS_24,
+  '5': CHANNELS_5,
+  '6': CHANNELS_6,
+};
+
+export const BAND_LABEL: Record<RfBand, string> = {
+  '2.4': '2.4 GHz',
+  '5': '5 GHz',
+  '6': '6 GHz',
+};
+
+/** Classify a frequency (MHz) into a coarse RF band, or null if unrecognized. */
+export function bandForFreq(freq: number): RfBand | null {
+  if (freq >= 2400 && freq < 2500) return '2.4';
+  if (freq >= 4900 && freq < 5925) return '5';
+  if (freq >= 5925 && freq <= 7125) return '6';
+  return null;
+}
+
+/** Convert a frequency (MHz) to its channel number for the appropriate band. */
+export function channelForFreq(freq: number): number | null {
+  const band = bandForFreq(freq);
+  if (band === '2.4') return freq === 2484 ? 14 : Math.round((freq - 2407) / 5);
+  if (band === '5') return Math.round((freq - 5000) / 5);
+  if (band === '6') return Math.round((freq - 5950) / 5);
+  return null;
+}
+
+/** Parse a RouterOS channel-width string to its width in MHz (best effort). */
+export function widthMhz(width: string | undefined): number {
+  if (!width) return 20;
+  const m = width.match(/(\d+)/);
+  const n = m ? parseInt(m[1], 10) : 20;
+  // RouterOS strings like "20/40/80mhz" report the smallest first; take the max present.
+  const all = (width.match(/\d+/g) || []).map(Number).filter(v => v >= 20 && v <= 160);
+  return all.length ? Math.max(...all) : (n >= 20 ? n : 20);
+}
+
+// ─── RSSI density helpers ──────────────────────────────────────────────────
+
+export interface RssiBand { label: string; min: number; max: number; color: string }
+
+// Signal-quality zones across the −90…−30 dBm scale (weak → excellent).
+export const RSSI_ZONES: RssiBand[] = [
+  { label: 'Poor',      min: -100, max: -80, color: '#ef4444' },
+  { label: 'Fair',      min: -80,  max: -70, color: '#f59e0b' },
+  { label: 'Good',      min: -70,  max: -60, color: '#84cc16' },
+  { label: 'Excellent', min: -60,  max: -20, color: '#22c55e' },
+];
+
+export function rssiColor(dbm: number): string {
+  for (const z of RSSI_ZONES) if (dbm >= z.min && dbm < z.max) return z.color;
+  return dbm >= -20 ? '#22c55e' : '#ef4444';
+}
+
+// ─── TX-retry histogram buckets (mirrors UniFi's 0%..35%+ scale) ─────────────
+
+export interface RetryBucket { label: string; min: number; max: number }
+export const RETRY_BUCKETS: RetryBucket[] = [
+  { label: '0%',   min: 0,  max: 2.5 },
+  { label: '5%',   min: 2.5, max: 7.5 },
+  { label: '10%',  min: 7.5, max: 12.5 },
+  { label: '15%',  min: 12.5, max: 17.5 },
+  { label: '20%',  min: 17.5, max: 22.5 },
+  { label: '25%',  min: 22.5, max: 30 },
+  { label: '35%+', min: 30,  max: 101 },
+];
+
+export function retryBucketIndex(pct: number): number {
+  for (let i = 0; i < RETRY_BUCKETS.length; i++) {
+    if (pct >= RETRY_BUCKETS[i].min && pct < RETRY_BUCKETS[i].max) return i;
+  }
+  return RETRY_BUCKETS.length - 1;
+}
+
+/** Color for a retry %: green (low) → red (high). */
+export function retryColor(pct: number): string {
+  if (pct < 5) return '#22c55e';
+  if (pct < 10) return '#84cc16';
+  if (pct < 20) return '#f59e0b';
+  return '#ef4444';
+}