feat: 3D hovering transparent VPS server rack schematic (#249)

Adds a procedural holographic server rack schematic to the Nexus scene:
- Transparent enclosure box with glowing cyan wireframe edges
- 12 stacked 1U server slab units with slot edge highlights
- Per-slot LED status indicators (green/blue/amber) with async blink phases
- Vertical mounting rails on front face
- Floating label sprite showing "VPS SERVER RACK / 143.198.27.163"
- Interior point glow light
- Animation: gentle hover float, subtle Y-axis sway, pulsing edge opacity,
  blinking LEDs, and breathing interior glow

Fixes #249

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app.js

@@ -656,6 +656,148 @@ for (let i = 0; i < RUNE_COUNT; i++) {
   runeSprites.push({ sprite, baseAngle, floatPhase: (i / RUNE_COUNT) * Math.PI * 2 });
 }
 
+// === VPS SERVER RACK SCHEMATIC ===
+// Hovering transparent holographic schematic of the physical VPS hosting the Nexus.
+// Positioned to the right-front of the platform; gently floats and sways.
+
+const SERVER_RACK_COLOR = 0x00ccff;  // cyan-blue schematic tint
+const SERVER_RACK_DIM   = 0x001a2e;  // dark translucent face fill
+
+const serverRackGroup = new THREE.Group();
+serverRackGroup.position.set(7.2, 2.2, 3.5);
+
+const RACK_W = 0.6;
+const RACK_H = 2.4;
+const RACK_D = 0.5;
+
+// Translucent enclosure faces
+const enclosureMat = new THREE.MeshBasicMaterial({
+  color: SERVER_RACK_DIM,
+  transparent: true,
+  opacity: 0.1,
+  side: THREE.DoubleSide,
+  depthWrite: false,
+});
+const enclosureGeo = new THREE.BoxGeometry(RACK_W, RACK_H, RACK_D);
+serverRackGroup.add(new THREE.Mesh(enclosureGeo, enclosureMat));
+
+// Glowing wireframe outline of enclosure
+const enclosureEdgeMat = new THREE.LineBasicMaterial({
+  color: SERVER_RACK_COLOR,
+  transparent: true,
+  opacity: 0.85,
+});
+serverRackGroup.add(new THREE.LineSegments(new THREE.EdgesGeometry(enclosureGeo), enclosureEdgeMat));
+
+// Server slabs — stacked 1U units inside the rack
+const RACK_UNIT_H   = 0.12;
+const RACK_UNIT_GAP = 0.03;
+const RACK_UNIT_W   = RACK_W * 0.92;
+const RACK_UNIT_D   = RACK_D * 0.85;
+const RACK_UNIT_STEP = RACK_UNIT_H + RACK_UNIT_GAP;
+const RACK_UNIT_COUNT = 12;
+
+const rackUnitGeo     = new THREE.BoxGeometry(RACK_UNIT_W, RACK_UNIT_H, RACK_UNIT_D);
+const rackUnitEdgeGeo = new THREE.EdgesGeometry(rackUnitGeo);
+const rackUnitFaceMat = new THREE.MeshBasicMaterial({
+  color: 0x000d1a,
+  transparent: true,
+  opacity: 0.14,
+  side: THREE.DoubleSide,
+  depthWrite: false,
+});
+
+// LED status colors per slot
+const RACK_LED_COLORS = [
+  0x00ff88, 0x00ff88, 0x00ff88, 0x4488ff,
+  0x00ff88, 0x00ff88, 0xffcc00, 0x00ff88,
+  0x4488ff, 0x00ff88, 0x00ff88, 0x00ff88,
+];
+
+/** @type {Array<{mat: THREE.MeshBasicMaterial, phase: number}>} */
+const rackLeds = [];
+const rackUnitEdgeMats = [];
+
+const rackStartY = -(RACK_H / 2) + RACK_UNIT_H / 2 + 0.06;
+
+for (let i = 0; i < RACK_UNIT_COUNT; i++) {
+  const y = rackStartY + i * RACK_UNIT_STEP;
+
+  // Translucent slab
+  const slab = new THREE.Mesh(rackUnitGeo, rackUnitFaceMat.clone());
+  slab.position.y = y;
+  serverRackGroup.add(slab);
+
+  // Glowing slot edges
+  const edgeMat = new THREE.LineBasicMaterial({
+    color: SERVER_RACK_COLOR,
+    transparent: true,
+    opacity: 0.3,
+  });
+  const edgeLines = new THREE.LineSegments(rackUnitEdgeGeo, edgeMat);
+  edgeLines.position.y = y;
+  serverRackGroup.add(edgeLines);
+  rackUnitEdgeMats.push(edgeMat);
+
+  // LED indicator on front face
+  const ledColor = RACK_LED_COLORS[i % RACK_LED_COLORS.length];
+  const ledGeo = new THREE.SphereGeometry(0.018, 6, 6);
+  const ledMat = new THREE.MeshBasicMaterial({ color: ledColor, transparent: true, opacity: 0.9 });
+  const led = new THREE.Mesh(ledGeo, ledMat);
+  led.position.set(RACK_UNIT_W / 2 - 0.07, y, RACK_UNIT_D / 2 + 0.002);
+  serverRackGroup.add(led);
+  rackLeds.push({ mat: ledMat, phase: (i / RACK_UNIT_COUNT) * Math.PI * 2 });
+}
+
+// Rack mounting rails — two thin vertical bars on front face
+for (const xOffset of [-RACK_W / 2 + 0.04, RACK_W / 2 - 0.04]) {
+  const railGeo = new THREE.BoxGeometry(0.025, RACK_H * 0.96, 0.025);
+  const railMat = new THREE.MeshBasicMaterial({
+    color: SERVER_RACK_COLOR,
+    transparent: true,
+    opacity: 0.45,
+  });
+  const rail = new THREE.Mesh(railGeo, railMat);
+  rail.position.set(xOffset, 0, RACK_D / 2);
+  serverRackGroup.add(rail);
+}
+
+// Floating label sprite above the rack
+function createRackLabelTexture() {
+  const W = 256, H = 64;
+  const canvas = document.createElement('canvas');
+  canvas.width = W;
+  canvas.height = H;
+  const ctx = canvas.getContext('2d');
+  ctx.clearRect(0, 0, W, H);
+  ctx.font = 'bold 13px "Courier New", monospace';
+  ctx.fillStyle = '#00ccff';
+  ctx.textAlign = 'center';
+  ctx.fillText('VPS SERVER RACK', W / 2, 26);
+  ctx.font = '10px "Courier New", monospace';
+  ctx.fillStyle = '#336688';
+  ctx.fillText('143.198.27.163', W / 2, 46);
+  return new THREE.CanvasTexture(canvas);
+}
+
+const rackLabelMat = new THREE.SpriteMaterial({
+  map: createRackLabelTexture(),
+  transparent: true,
+  opacity: 0.85,
+  depthWrite: false,
+});
+const rackLabelSprite = new THREE.Sprite(rackLabelMat);
+rackLabelSprite.scale.set(2.4, 0.6, 1);
+rackLabelSprite.position.set(0, RACK_H / 2 + 0.45, 0);
+serverRackGroup.add(rackLabelSprite);
+
+// Interior glow
+const rackGlowLight = new THREE.PointLight(SERVER_RACK_COLOR, 0.35, 3.5);
+serverRackGroup.add(rackGlowLight);
+
+scene.add(serverRackGroup);
+const SERVER_RACK_BASE_Y = serverRackGroup.position.y;
+
 // === ANIMATION LOOP ===
 const clock = new THREE.Clock();
 
@@ -770,6 +912,15 @@ function animate() {
     rune.sprite.material.opacity = 0.65 + Math.sin(elapsed * 1.2 + rune.floatPhase) * 0.2;
   }
 
+  // Animate VPS server rack — hover float, subtle sway, LED blink
+  serverRackGroup.position.y = SERVER_RACK_BASE_Y + Math.sin(elapsed * 0.55 + 1.1) * 0.18;
+  serverRackGroup.rotation.y = Math.sin(elapsed * 0.13) * 0.07;
+  enclosureEdgeMat.opacity = 0.65 + Math.sin(elapsed * 1.0) * 0.2;
+  for (const { mat, phase } of rackLeds) {
+    mat.opacity = 0.55 + Math.sin(elapsed * 3.0 + phase) * 0.4;
+  }
+  rackGlowLight.intensity = 0.25 + Math.sin(elapsed * 1.5) * 0.12;
+
   composer.render();
 }