fix(ui): show read action on JS-rendered dashboard cards

The dashboard re-renders its sections client-side (library switch,
refresh, saving settings) via renderBookCard in dashboard.ts, which was
still the old markup with no .book-card-action overlay. So the read
button appeared on the server-rendered cards but vanished as soon as the
dashboard re-rendered, while the bookshelf (always templ-rendered) kept
working.

- Rewrite renderBookCard to match the templ BookCard: detail link plus
  the play/read action overlay, routing to the reader or the detail page
  when the book has an active conflict.
- Add has_conflict to the BookInfo TS type and stamp it in the dashboard
  sections API (GetSections) so client-rendered cards can route correctly.
- Add pointer-events-none / group-hover:pointer-events-auto to the
  client-rendered carousel nav buttons so they no longer swallow hover
  over edge cards, matching the templ fix.

internal/handlers/dashboard.go

@@ -65,6 +65,7 @@ func (h *DashboardHandler) GetSections(c *echo.Context) error {
 	}
 
 	sectionData := BuildSections(sections, libraryID)
+	sectionData = MarkActiveConflictsSections(c.Request().Context(), h.db, user.ID, sectionData)
 
 	return c.JSON(http.StatusOK, map[string]interface{}{"sections": sectionData})
 }