Use Companion's native Gauge element for level displays

Companion 5.1 marks image-buffer feedbacks as deprecated, and its layered
buttons have a Gauge element that follows a number directly. So:

- New numeric value feedbacks for gauges: fader/level position 0-100 for
  inputs, busses, matrix outputs, control groups, aux sends and matrix
  sends (one shared fader taper: 0 dB at 75 %, -inf at 0), raw pan 0..1
  for a symmetric gauge, GEQ band dB, and input meter position.
- Every knob and meter preset is now a layered preset: background box,
  channel name, live dB text and a Gauge bound to $(local:pos); on/off and
  mute tint the background. Meters use a vertical green/amber/red gauge.
  Text uses size 100 with shrink-to-fit (14 rendered tiny on 5.1) and the
  level gauge is white so it stays visible on a green background.
- The old image-bar feedbacks keep working and are labelled "(legacy
  image)"; HELP.md explains how to add a gauge to your own button.
- A sleeping iPad no longer logs a relay send error every few seconds:
  one warning per iPad per 10 minutes.

Checked on the booth Companion 5.1: the layered knob previews show live
names, levels and gauge fills. npm test: 392 checks pass.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/main.js

@@ -367,6 +367,18 @@ export default class DigicoS31Instance extends InstanceBase {
 		if (last !== undefined && now - last < this.timing.errorLogMs) return false
 		if (this.errorLog.size > 200) this.errorLog.clear()
 		this.errorLog.set(key, now)
+		// An iPad that went to sleep makes every fan-out fail with "host down/unreachable" until the relay forgets it
+		// (up to the idle timeout): say so once per iPad as a warning instead of an error every few seconds.
+		const asleep = source === 'Relay socket' && err.dest && ['EHOSTDOWN', 'EHOSTUNREACH', 'ENETUNREACH'].includes(err.code)
+		if (asleep) {
+			const ip = String(err.dest).split(':')[0]
+			const sleepKey = `asleep|${ip}`
+			const lastSleep = this.errorLog.get(sleepKey)
+			if (lastSleep !== undefined && now - lastSleep < 10 * 60 * 1000) return false
+			this.errorLog.set(sleepKey, now)
+			this.log('warn', `Relay: iPad ${ip} is not reachable (asleep or off the network); it stays on the list until it sends again or the idle timeout passes`)
+			return true
+		}
 		this.log('error', `${source}: ${err.message}${err.dest ? ` (${err.dest})` : ''}`)
 		return true
 	}