Library: "Continue where you left off" row with a per-user setting

One fixed row above the library showing the five most recently read,
unfinished manga with the normal tiles (they stay in the grid as well).
It ignores search and filters, hides while sorted by "Recently read",
and can be turned off under Settings > Reading > Library page
(continueRow, default on).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -142,6 +142,7 @@ completeness.
 - **Flow page gap:** Settings → Reading lets each user keep the normal separator between Flow pages or remove it for continuous webtoon artwork and text that crosses image edges.
 - **Page tone:** the reader's **Tone** button cycles Original → Inverted → Sepia → Dim → Extra dim in Flow, Page and Book. It changes only the artwork, never the controls or site theme. The choice is saved per user; it can also be selected in Settings → User → Reading.
 - **Active Reading Clock:** opt in under Settings → User → Reading time & privacy. No scrolling-speed limit; a visit counts at 60% viewed-page coverage and saves on exit. Pauses in the background or after 30 seconds without reader activity. Tap the clock for this visit's time, coverage, qualification and loading wait.
+- **Continue where you left off:** the library opens with one row of the five manga you read most recently and have not finished (same tiles as the grid; they stay in the grid too). The row ignores the search and filters and hides while the library is sorted by *Recently read*. Turn it off under Settings → User → Reading → *Library page*.
 - **Your Reading Story:** private active-time summaries appear on the library and manga pages when history exists. Chapter rows show the last timed read (60%-coverage visit), rereads remain visible as lifetime time, and Settings lets each user hide, export, or delete their own history. No leaderboards or speed ranking are used.
 - **Tap / click zones:**
   - Tapping **beside the pages** always shows or hides the controls.