Refactor App loader logic and add MetadataLoader

Replaces custom route matching and file loading in App.tsx with a pluggable MetadataLoader strategy, supporting both local bundle and network API loading. Introduces MetadataLoader, LocalBundleLoader, and NetworkLoader classes for modular metadata access. Removes obsolete router logic and improves error handling. Also deletes the outdated implementation-status.md documentation.

Author: hotlong