軽量なインタラクティブ粒子背景

Implement a reusable ambient particle background for {{service}} with a {{style}} visual style. Choose Canvas 2D for simple flat particles or reuse the existing Three.js stack when true depth is needed; explain the choice. Use slow coherent motion and a subtle attraction or repulsion response to a pointer, with a touch-safe behavior that does not block scrolling. Expose particle count, speed, interaction radius and {{palette}} colors. Keep the main content legible and all decorative rendering pointer-transparent. Adapt particle count and device pixel ratio to an explicit quality preset, with reasonable upper bounds.

Implementation constraints:
First inspect the existing repository and installed versions. Reuse its routing, styling, build tools and dependency conventions. Use React Three Fiber only if the project already uses it or the integration is clearly justified; otherwise use the existing Three.js integration or a minimal isolated component. Do not assume version-specific APIs: check the installed package documentation and types. Do not change unrelated pages or silently replace the application architecture. Explain any required new dependency before adding it. Dispose GPU resources, remove event listeners and stop rendering when the component is not visible. Respect prefers-reduced-motion and provide a readable non-WebGL fallback. Keep links and controls in accessible HTML above the canvas. Return the changed files, configuration knobs, tests performed and known limitations.

Acceptance criteria:
- Pointer effects do not consume touch scroll gestures or block links.
- No animation loop runs when the component is unmounted or the page is hidden.
- Reduced-motion mode uses a static background and no pointer-driven movement.
- Particle buffers are reused rather than allocated every frame.
- Provide a static fallback and report measured performance at the selected maximum particle count.