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_zh.arb

@@ -207,5 +207,18 @@
   "@diagExported": { "placeholders": { "bytes": { "type": "int" } } },
   "diagExportFail": "导出失败：{error}",
   "@diagExportFail": { "placeholders": { "error": { "type": "String" } } },
-  "processingOcr": "正在识别文字…"
+  "processingOcr": "正在识别文字…",
+  "notebooksSection": "笔记本",
+  "addBlankPage": "空白页",
+  "importIntoNotebook": "导入到笔记本",
+  "notebookMembersEmpty": "还没有页面",
+  "memberCount": "{count} 项",
+  "@memberCount": {
+    "placeholders": { "count": { "type": "int" } }
+  },
+  "textFontSmall": "小",
+  "textFontMedium": "中",
+  "textFontLarge": "大",
+  "textBold": "粗体",
+  "textDragHint": "拖动移动"
 }