feat(frontend): mobile catalog with sheet filters + sort (0.57.0)

Phase 2 of the mobile redesign: the catalog at `/` adapts to phone
viewports without disrupting the desktop layout. The same filter form
renders inline on desktop and inside a bottom sheet on mobile, and a
dedicated sort sheet replaces the inline `<select>` below 640px.

- MangaCard gains optional `unreadCount` and `progress` props that
  render a top-right pill badge and a bottom progress overlay on the
  cover. Both are no-ops when omitted, so existing callers don't
  change. Counts past 99 cap at "99+".
- The filter form body is extracted into a Svelte 5 snippet and
  rendered conditionally — inline desktop panel OR mobile sheet, never
  both — so no testid is duplicated and the focus trap can't double-
  fire. A matchMedia listener tracks the 640px breakpoint and drives
  the snippet target.
- Mobile catalog adds: Filter / Sort chip buttons, an always-visible
  active-filter chip row with per-facet remove buttons, full-width
  search, and a 2-column grid.
- Auto-expanding the filter panel from URL params is now desktop-only
  — on mobile the active-filter chips signal applied facets without
  hiding the catalog under a scrim on first paint.
- Vitest suite covers MangaCard badge / overlay behavior including
  clamp / hide edge cases. Playwright spec covers the mobile filter +
  sort sheet flow at 390px viewport, with a hydration gate to keep
  click dispatch from racing the SSR'd-but-not-yet-reactive button.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mangalord"
-version = "0.56.0"
+version = "0.57.0"
 edition = "2021"
 default-run = "mangalord"