Revert "Revert LCD/pot to always-visible with placeholder values when disconnected"

This reverts commit 975c9c97ef.

web/app.js

@@ -743,6 +743,7 @@ function setConnected(isConnected) {
 	const statusEl = document.getElementById('conn-status');
 	statusEl.textContent = isConnected ? 'Connected' : 'Disconnected';
 	statusEl.className = isConnected ? 'status-connected' : 'status-disconnected';
+	document.getElementById('lcd-pot-row').style.visibility = isConnected ? 'visible' : 'hidden';
 	document.getElementById('sud-status-line').style.visibility = isConnected ? 'visible' : 'hidden';
 	document.getElementById('env-status-line').style.visibility = isConnected ? 'visible' : 'hidden';
 	updateSudActions();

web/style.css

@@ -142,6 +142,7 @@ header#connection-bar {
     gap: 1.5em;
     margin: 1em 0;
     font-size: 2em;
+    visibility: hidden;
 }
 
 /* --- Pot visualization --- */