feat: add portal status field with visual health indicators

Add `status` field to portals.json (online/offline/maintenance).
Portal ring emissive intensity dims for non-online portals (1.5→0.3).
Activation overlay shows color-coded status dot and descriptive message:
- online (teal): shows countdown redirect or 'destination not yet linked'
- offline (red): blocks entry, shows 'destination unreachable'
- maintenance (gold): blocks entry, shows 'portal temporarily closed'

Refs #5

app.js

@@ -560,6 +560,9 @@ function createPortalMesh(cfg) {
   const ringEmit = new THREE.Color(cfg.ringEmissive);
   const pCol = new THREE.Color(cfg.particleColor);
 
+  const isOnline = !cfg.status || cfg.status === 'online';
+  const emissiveStrength = isOnline ? 1.5 : 0.3;
+
   const portalGroup = new THREE.Group();
   portalGroup.position.set(...cfg.position);
   portalGroup.rotation.y = cfg.rotationY;
@@ -570,7 +573,7 @@ function createPortalMesh(cfg) {
   const torusMat = new THREE.MeshStandardMaterial({
     color: ringCol,
     emissive: ringEmit,
-    emissiveIntensity: 1.5,
+    emissiveIntensity: emissiveStrength,
     roughness: 0.2,
     metalness: 0.8,
   });
@@ -1039,23 +1042,38 @@ function activatePortal(entry) {
   overlay.style.display = 'flex';
   overlay.classList.remove('fade-out');
 
+  const portalStatus = entry.config.status || 'online';
+  const statusColors = { online: '#4af0c0', offline: '#ff4466', maintenance: '#ffd700' };
+  const statusColor = statusColors[portalStatus] || entry.config.ringColor;
+  status.style.color = statusColor;
+
+  if (portalStatus === 'offline') {
+    status.textContent = '● OFFLINE — destination unreachable';
+    return;
+  }
+  if (portalStatus === 'maintenance') {
+    status.textContent = '● MAINTENANCE — portal temporarily closed';
+    return;
+  }
+
   const url = entry.config.destination?.url;
   if (url) {
+    status.textContent = '● ONLINE';
     let countdown = 3;
-    status.textContent = `Opening portal in ${countdown}s…`;
+    status.textContent = `● ONLINE — Opening portal in ${countdown}s…`;
     const iv = setInterval(() => {
       countdown--;
       if (countdown <= 0) {
         clearInterval(iv);
-        status.textContent = 'Entering…';
+        status.textContent = '● ONLINE — Entering…';
         window.location.href = url;
       } else {
-        status.textContent = `Opening portal in ${countdown}s…`;
+        status.textContent = `● ONLINE — Opening portal in ${countdown}s…`;
       }
     }, 1000);
     btn.dataset.intervalId = iv;
   } else {
-    status.textContent = 'Portal active — destination not yet linked';
+    status.textContent = '● ONLINE — destination not yet linked';
   }
 
   btn.onclick = () => {

portals.json

@@ -4,6 +4,7 @@
       "id": "morrowind",
       "label": "◈ MORROWIND",
       "description": "The Elder Scrolls III — Vvardenfell awaits",
+      "status": "online",
       "position": [15, 0, -10],
       "rotationY": -0.5,
       "ringColor": "#ff6600",
@@ -22,6 +23,7 @@
       "id": "bannerlord",
       "label": "⚔ BANNERLORD",
       "description": "Mount & Blade II — The Calradic Empire calls",
+      "status": "online",
       "position": [-15, 0, -10],
       "rotationY": 0.5,
       "ringColor": "#cc7700",
@@ -40,6 +42,7 @@
       "id": "workshop",
       "label": "⚙ WORKSHOP",
       "description": "The Forge — Build, create, iterate without limits",
+      "status": "online",
       "position": [0, 0, 18],
       "rotationY": 3.14159,
       "ringColor": "#00ccaa",