Add ML-assisted Myspace capture classification

[SahilKumar75]

Summary

Add a Myspace classification path that can assign saved captures into stable categories such as note, timetable, screenshot, link, file, or study material.

Scope

• Define a lightweight classification contract between the app and ML worker.
• Add deterministic fallback rules so classification works without a model service.
• Add fixtures for common Myspace capture inputs.
• Keep user-facing behavior explainable.

Acceptance Criteria

• Myspace saved items can receive a normalized capture category.
• The ML worker has tests or fixtures for representative inputs.
• The app integration path is documented or stubbed clearly.
• The PR explains how classification confidence is derived.