feat: AniList reading status integration

- Add full AniList integration: OAuth connect, series linking, push/pull sync
- Push: PLANNING/CURRENT/COMPLETED based on books read vs total_volumes (never auto-complete from owned books alone)
- Pull: update local reading progress from AniList list (per-user)
- Detailed sync/pull reports with per-series status and progress
- Local user selector in settings to scope sync to a specific user
- Rename "AniList" tab/buttons to generic "État de lecture" / "Reading status"
- Make Bédéthèque and AniList badges clickable links on series detail page
- Fix ON CONFLICT error on series link (provider column in PK)
- Migration 0054: fix series_metadata missing columns (authors, publishers, locked_fields, total_volumes, status)
- Align button heights on series detail page; move MarkSeriesReadButton to action row

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/backoffice/app/components/ExternalLinkBadge.tsx

@@ -0,0 +1,21 @@
+"use client";
+
+interface ExternalLinkBadgeProps {
+  href: string;
+  className?: string;
+  children: React.ReactNode;
+}
+
+export function ExternalLinkBadge({ href, className, children }: ExternalLinkBadgeProps) {
+  return (
+    <a
+      href={href}
+      target="_blank"
+      rel="noopener noreferrer"
+      className={className}
+      onClick={(e) => e.stopPropagation()}
+    >
+      {children}
+    </a>
+  );
+}