fix(relays): {value} is the relay's label, not a per-relay value

It was built the other way round on a misreading of two screenshots: the pattern
held {value} and the per-relay boxes held numbers to drop into it. The ask was
simpler and better — {value} is the name typed in Relay labels, so a switch
addressed by antenna name is one pattern instead of eight URLs:

  http://10.10.10.100/relay?on={value}   relay 1 named Ant1  →  ?on=Ant1

Renaming the antenna re-addresses it, and the name on the button and the name on
the wire cannot drift apart because they are the same string. It works in the
per-relay URLs and in the patterns alike, so the per-relay boxes go back to
holding URLs and nothing about them changes meaning any more.

The label is percent-encoded with %20 rather than "+" for a space: "+" is a
space only in a query string and a literal plus in a path, and this can land in
either half of a URL.

{value} on a relay with no label would send "?on=", an empty parameter that most
boards answer with a cheerful 200 and no movement. The driver refuses it and
names the label as what is missing; the editor warns while it is being typed,
beside the empty box rather than after an antenna fails to switch. The labels
also join the driver's cache key — they are part of the wire format now.

app.go

@@ -14763,7 +14763,7 @@ func buildDeviceDriver(d StationDevice) relaydev.Device {
 		// generic board fall through to the WebSwitch driver below: it answered
 		// the WebSwitch's own address, never sent one configured URL, and
 		// reported itself offline so every relay button stayed greyed out.
-		return relaydev.NewHTTPGeneric(d.OnURLs, d.OffURLs, d.OnPat, d.OffPat, d.User, d.Pass, deviceRelayCount(d))
+		return relaydev.NewHTTPGeneric(d.OnURLs, d.OffURLs, d.OnPat, d.OffPat, d.User, d.Pass, deviceRelayCount(d), d.Labels)
 	default:
 		return relaydev.NewWebswitch(d.Host)
 	}
@@ -14779,7 +14779,11 @@ func deviceKey(d StationDevice) string {
 		// handed back the cached driver still holding the wrong address, so the
 		// fix appeared to do nothing until OpsLog was restarted.
 		k += "|" + d.OnPat + "|" + d.OffPat +
-			"|" + strings.Join(d.OnURLs, "\x1f") + "|" + strings.Join(d.OffURLs, "\x1f")
+			"|" + strings.Join(d.OnURLs, "\x1f") + "|" + strings.Join(d.OffURLs, "\x1f") +
+			// The labels are part of the wire format here: {value} sends them.
+			// Renaming a relay re-addresses it, and the cached driver would keep
+			// commanding the old name.
+			"|" + strings.Join(d.Labels, "\x1f")
 	}
 	return k
 }