feat: admin UX overhaul — status filters, retry/cancel, mobile cards, i18n, shelf pre-populate

- Admin layout: SVG icons, active highlight, divider between nav sections
- Scrape page: status filter pills with counts, text + status combined search
- Audio page: status filter pills, cancel jobs, retry failed jobs, mobile cards for cache tab
- Translation page: status filter pills (incl. cancelled), cancel + retry jobs, mobile cancel/retry cards, i18n for all labels
- AI Jobs page: fix concurrent cancel (Set instead of single slot), per-job cancel errors inline, full mobile card layout, i18n title/heading
- Text-gen page: tagline editable input + copy, warnings copy, i18n title/heading
- Book page: chapter cover Save button, audio monitor link, currentShelf pre-populated from server
- pocketbase.ts: add getBookShelf(), shelf field on UserLibraryEntry
- New API route: POST /api/admin/translation/bulk (proxy for translation retry)
- i18n: 15 new admin_translation_*, admin_ai_jobs_*, admin_text_gen_* keys across all 5 locales

ui/src/lib/server/pocketbase.ts

@@ -646,6 +646,7 @@ export interface UserLibraryEntry {
 	user_id?: string;
 	slug: string;
 	saved_at: string;
+	shelf?: string;
 }
 
 function libraryFilter(sessionId: string, userId?: string): string {
@@ -675,6 +676,19 @@ export async function isBookSaved(
 	return row !== null;
 }
 
+/** Returns the shelf the user has placed this book on, or '' if not saved / no shelf set. */
+export async function getBookShelf(
+	sessionId: string,
+	slug: string,
+	userId?: string
+): Promise<ShelfName> {
+	const filter = userId
+		? `user_id="${userId}"&&slug="${slug}"`
+		: `session_id="${sessionId}"&&slug="${slug}"`;
+	const row = await listOne<UserLibraryEntry>('user_library', filter).catch(() => null);
+	return (row?.shelf as ShelfName) || '';
+}
+
 /** Save a book to the user's library. No-op if already saved. */
 export async function saveBook(
 	sessionId: string,