chore: migrate to ESLint config v3

[kpal81xd]

Part of playcanvas/eslint-config#48.

Scope

• Migrates from ESLint config v2 to 3.0.0-beta.8 with the TypeScript and React presets, shared Prettier formatting, and CI type checking.
• Replaces explicit any annotations and legacy suppressions with sound DOM, loader, asset-module, and property-value types without weakening no-explicit-any.
• Preserves application behavior: formatting and type-only edits erase at runtime; the remaining ownership checks and import ordering retain existing semantics.

Manual smoke test

1. Serve this branch locally and open https://playcanvas.com/viewer/?use_local_frontend through the local-frontend override. The Model Viewer shell and canvas should initialize.
2. Load a GLB URL. The model should render and the scene statistics and hierarchy should populate.
3. Pause and resume animation, orbit the camera, switch between orbit and fly modes, and select a hierarchy node. Each control should update the viewport.
4. Change FOV and select ACES tone mapping. The observer and camera should apply both settings without Model Viewer console errors.