fix(core): retain mesh background during async album loads

[LuorixDev]

Summary

• Ignore stale album-load completions and abort the previous fetch when a new cover is requested.
• Preserve the currently rendered mesh when the latest cover fails to load.
• Recreate WebGL programs, buffers, framebuffer resources, mesh, and texture after context restoration using the last successful album pixels.

Root cause

Concurrent setAlbum calls shared isNoCover state. A failed request for an older cover could mark the renderer as having no cover after a newer cover had already loaded, which faded out the visible background. The renderer also had no context-loss recovery path.

Validation

• pnpm --filter @applemusic-like-lyrics/core typecheck
• pnpm --filter @applemusic-like-lyrics/core build
• biome lint packages/core/src/bg-render/mesh-renderer/index.ts --error-on-warnings
• git diff --check

[LuorixDev]

修有时候背景是黑色的bug