Rebuild Emotion Explorer 3D experience (CSS-driven scene & HUD)

[ryanmmmmm]

Motivation

• Replace the prior Three.js-based attempt with a self-contained, CSS/Canvas-driven 3D-styled game scene to avoid dependency and install issues while delivering a rich interactive vista.

Description

• Add a new interactive component EmotionExplorer3D that renders a layered floating-island scene, an animated canvas starfield, orbiting emotion orbs, pointer-driven tilt, and an on-screen HUD (frontend/src/components/EmotionExplorer3D.tsx).
• Expand and add styles to support the scene (frontend/src/styles/global.css) including starfield canvas, horizon transforms, island layers, orbital elements, arches, tower beam animation, and HUD meter visuals.
• Wire the scene into the app by adding the /emotion-explorer-3d route and a navigation tile/menu entry in App.tsx and Layout.tsx so the scene is reachable from the UI.
• Remove unused 3D engine runtime dependencies (@react-three/*, three, postprocessing) from frontend/package.json since the scene no longer relies on them, and fix a CSS parsing bug in TrajectoriesScene by consolidating the background line and adding backgroundRepeat.

Testing

• Started the dev server with npm run dev -- --host 0.0.0.0 --port 4173 and the server came up successfully and served the app at the expected address.
• Performed an automated visual check using a Playwright script that opened http://127.0.0.1:4173/emotion-explorer-3d and saved a screenshot (artifacts/emotion-explorer-3d.png), which completed successfully.
• No unit tests were added; changes were validated via the running dev server and the screenshot-based visual review.

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Codex Task