Fix builtin effect loading for scene previews

[bofeng-song]

Summary

• Add an internal scene EffectService that mirrors Creator's effect manager: query all cc.EffectAsset entries and load them through assetManager.loadAny before preview services initialize.
• Move browser asset fallback setup before service initialization so the effect service can load internal/project effect assets in scene-editor preview.
• Keep material and mesh preview guards so missing effect passes degrade gracefully instead of crashing.

Testing

• git diff --check cli/main...HEAD
• npx tsc -b --pretty false
• npx jest src/core/scene/test/scene.middleware.test.ts src/core/preview/test/scripting-routes.test.ts src/core/scene/test/service-core/service-manager-forwarding.test.ts --runInBand