chore: code quality audit and lint fixes

- Fix all 63 ESLint errors across codebase
- Consolidate MaterialWithTextureSlots type in src/types/three/three.ts
- Add CSS custom properties for design tokens
- Extract ebike constants to src/data/ebike/ebikeConfig.ts
- Add proper TypeScript types for window extensions
- Fix React hooks violations (refs during render, setState in effects)
- Remove unused exports and redundant CSS
- Add type guards for Three.js material handling
- Clean up AI slop comments and legacy CSS patterns

src/world/GameCinematics.tsx

@@ -181,10 +181,12 @@ function playCinematic(
 let cameraTransitionTimeline: gsap.core.Timeline | null = null;
 let globalCamera: THREE.Camera | null = null;
 
+// eslint-disable-next-line react-refresh/only-export-components
 export function setGlobalCamera(camera: THREE.Camera | null): void {
   globalCamera = camera;
 }
 
+// eslint-disable-next-line react-refresh/only-export-components
 export function animateCameraTransition(
   targetPosition: Vector3Tuple,
   targetLookAt: Vector3Tuple,
@@ -234,6 +236,7 @@ export function animateCameraTransition(
   );
 }
 
+// eslint-disable-next-line react-refresh/only-export-components
 export function animateCameraTransformTransition(
   targetPosition: Vector3Tuple,
   targetRotation: Vector3Tuple,