docs: Add Phase 15 (3D Visualization) to Roadmap

- Added spec for 'Cool 3D Views' using react-three-fiber
- Planned features: 3D volumes, tier stacking, walking mode

docs/ROADMAP.md

@@ -350,6 +350,22 @@ Integrate physical security and monitoring systems (RTSP/ONVIF cameras) directly
   - "Security Overview" dashboard widget
   - Map integration (cameras on Layout Designer)
 
+## 🚀 Phase 15: 3D Facility Visualization (The "Cool Views")
+
+### Goal
+
+Deliver the "SketchUp-like" experience by rendering the facility layout in an immersive 3D view.
+
+### Sprint 1: 3D Viewer [ROADMAP]
+
+- **Tech Stack**: `react-three-fiber` (Three.js)
+- **Features**:
+  - Render buildings, floors, rooms as 3D volumes
+  - Render tables/racks with correct tier stacking
+  - First-person "Walking" mode
+  - "God View" (Orbit controls)
+  - Visualizing plant health/status as colored blocks
+
 ---
 
 ## 📊 Roadmap Timeline (Proposed)
@@ -364,6 +380,7 @@ Integrate physical security and monitoring systems (RTSP/ONVIF cameras) directly
 | Phase 12: Hardware Integration | 2-4 weeks | 🟡 Medium |
 | Phase 13: Advanced Features | Ongoing | 🟢 Future |
 | Phase 14: Facility Monitoring | Roadmapped | 🟢 Future |
+| Phase 15: 3D Visualization | Roadmapped | 🟢 Future |
 
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