feat: OneNote-style notebooks, text fonts, and page navigation

Add notebook.json containers with multi-member pages, fix PDF text
editing (size/bold/drag/double-tap), index SidecarText in search, and
share keyboard page shortcuts plus a PDF scrubber.

Co-authored-by: Cursor <cursoragent@cursor.com>

lib/l10n/app_localizations_en.dart

@@ -588,4 +588,36 @@ class AppLocalizationsEn extends AppLocalizations {
 
   @override
   String get processingOcr => 'Processing OCR…';
+
+  @override
+  String get notebooksSection => 'Notebooks';
+
+  @override
+  String get addBlankPage => 'Blank page';
+
+  @override
+  String get importIntoNotebook => 'Import into notebook';
+
+  @override
+  String get notebookMembersEmpty => 'No pages yet';
+
+  @override
+  String memberCount(int count) {
+    return '$count items';
+  }
+
+  @override
+  String get textFontSmall => 'S';
+
+  @override
+  String get textFontMedium => 'M';
+
+  @override
+  String get textFontLarge => 'L';
+
+  @override
+  String get textBold => 'Bold';
+
+  @override
+  String get textDragHint => 'Drag to move';
 }