feat: added "sort by date finished" for Already Readed books

[akramcodez]

Closes #11336

Changes

Controller (mybooks.py):

• Accepts the new order_by parameter (either created or finished).
• Passes sort choice through to the reading log/business logic.
• Normalizes sort types for backend compatibility.

Database Layer (bookshelves.py):

• Expands sort logic to support finished asc/desc alongside created.
• Pads partial dates (year, year+month) for correct sorting.
• Books without a finish date are ordered last (when sorting descending) or first (when sorting ascending).
• SQL sorts by: padded finish date → specificity → date added, as outlined in the issue.

UI Template (reading_log.html):

• Adds four sort options (Date Added: newest/oldest, Date Finished: newest/oldest) for “Already Read” shelf.
• Highlights the currently active sort choice.
• Other shelves retain two sort options.

Screen Recoding

https://github.com/user-attachments/assets/ee42e394-7a76-4a12-8540-24b873f69a55

Stakeholders

@mekarpeles

[akramcodez]

@mekarpeles please let me know if there’s any issue.