[Feature Request] Add web UI book metadata editor (genres, moods, content warnings, description) #32

Context & Problem Statement

CrossPoint Sync features statistics and visual insights based on book metadata—such as Moods and Genres charts.

However, many books in a user's library have incomplete or missing metadata. Currently, there is no way for users to edit or fill in this metadata directly within the web UI. As a result, books with missing genres or moods lead to inaccurate or incomplete statistics visualizations.

Proposed Feature

Introduce book entry metadata editor on the book details page, enabling users to manually edit, add, or update book metadata fields.

Key Requirements

1. Editable Metadata Fields:

   • Genres & Moods: Allow users to add/remove genre tags and mood attributes so they populate the statistics engine.

2. Statistics Integration:

   • Automatically update and recalculate user reading insights and distribution charts (Moods & Genres) when book metadata is modified.

3. User Experience:

   • Provide an "Edit Metadata" button on the book details page with a simple tag/input form.
   • (Optional) Include an auto-fetch / suggestions button from online databases (e.g., Hardcover, OpenLibrary) to populate missing fields automatically.