Add reading progress and recently opened books

[KrapfalAT]

Summary

• Reading progress bar appears at the bottom of each book row in the system view, filling up as you read further into the book
• Last read page number is shown next to the page count (e.g. p. 42)
• "Recently Opened" section appears at the top of the library page showing the last 10 opened books as compact cards
• clicking one jumps straight back to the last read page

Notes

Progress and recently opened data is stored in localStorage per book (grimoire:book:{id}). The reader was already saving the last read page — this PR just surfaces that data in the UI. No backend changes required.

[hunter-read]

Thanks for the PR, I'll be taking a look at this tonight when I have more time to validate.