HUD overlay + live data fix + camera controls
Fixed live data fetch failing on datadrift.art — added `VITE_API_KEY` to Vercel environment variables and redeployed. Repositioned camera to face all three particle cluster centers, placed along the plane normal of the cluster triangle.
Built HTML/CSS HUD overlay: live PM₂.₅, PM₁₀, NO₂, CO bars with actual μg/m³ values, sensitivity indicator with state label (Sensitized / Adapting / Normalized), and dynamic reaction text describing organism behaviour. Added `?` toggle button to show/hide HUD, nav hint at bottom center that fades on first interaction. Implemented arrow key camera rotation via spherical coordinate manipulation. Enabled particle system (was previously hidden).
Working: Live data displaying correctly in HUD on both localhost and datadrift.art. Arrow keys rotate camera smoothly alongside mouse drag. HUD panel opens and closes cleanly. Reaction text updates dynamically based on dominant pollutant and sensitivity state. Particles visible and clustering as expected.
Next: Continue refining visual and UI system.