feat(ui): rebuild shared chrome and core browse/read pages

- Header: sticky app-wide, active nav highlighting, data-driven theme
  picker with active swatch, unified SVG icons, deduped login fragment
  (was duplicated verbatim for desktop + mobile), removed stray console.log
- LibrarySwitcher: cleaner sticky bar, SVG action icons, theme-aware
- BookCard: the atomic unit now has a real surface (was floating text
  when wood-paneling was off due to an undefined --wood-border), with
  cohesive shadow + hover lift; reused across dashboard/bookshelf/series
- Dashboard: calmer section headers, snap carousels with SVG chevrons
- Bookshelf: recompose the filter wall into a search toolbar + collapsible
  Filters panel (all 9 filters + save/load/clear preserved), redesigned
  empty state and pagination
- Book detail, series, collections, browse: cohesive cards, SVG action
  icons, uppercase muted labels, theme-aware badges/links

templates/books_grid.templ

@@ -8,10 +8,12 @@ templ BooksGrid(books []handlers.BookInfo, limit int, offset int, count int, cur
 				@BookCard(book)
 			}
 		} else {
-			<!-- Empty state -->
-			<div class="col-span-full text-center py-12" style="color: var(--text-secondary);">
-				<p class="text-lg mb-2">📚 No books found</p>
-				<p class="text-sm">Try adjusting your filters or add some books to your library.</p>
+			<div class="col-span-full flex flex-col items-center justify-center rounded-2xl border border-dashed border-line py-16 text-center">
+				<div class="mb-3 flex h-14 w-14 items-center justify-center rounded-full bg-surface-hover text-content-muted">
+					@Icon("book", "h-7 w-7")
+				</div>
+				<p class="text-base font-semibold text-content">No books found</p>
+				<p class="mt-1 text-sm text-content-muted">Try adjusting your filters or add some books to your library.</p>
 			</div>
 		}
 }