docs: update TOC in userguide (#2479)

USER_GUIDE.md

@@ -5,6 +5,7 @@ Welcome to the **CrossPoint** firmware. This guide outlines the hardware control
 - [CrossPoint User Guide](#crosspoint-user-guide)
   - [1. Hardware Overview](#1-hardware-overview)
     - [Button Layout](#button-layout)
+    - [Taking a Screenshot](#taking-a-screenshot)
   - [2. Power \& Startup](#2-power--startup)
     - [Power On / Off](#power-on--off)
     - [First Launch](#first-launch)
@@ -14,7 +15,11 @@ Welcome to the **CrossPoint** firmware. This guide outlines the hardware control
     - [3.3 Browse Files Screen](#33-browse-files-screen)
     - [3.4 Recent Books Screen](#34-recent-books-screen)
     - [3.5 File Transfer Screen](#35-file-transfer-screen)
-      - [3.5.1 Calibre Wireless Transfers](#351-calibre-wireless-transfers)
+    - [3.5.1 Calibre Wireless Transfers](#351-calibre-wireless-transfers)
+      - [Installing the Plugin in Calibre](#installing-the-plugin-in-calibre)
+      - [Configuring the CrossPoint Plugin in Calibre](#configuring-the-crosspoint-plugin-in-calibre)
+      - [Uploading Books](#uploading-books)
+      - [Removing a Book](#removing-a-book)
     - [3.6 Settings](#36-settings)
       - [3.6.1 Display](#361-display)
       - [3.6.2 Reader](#362-reader)
@@ -23,21 +28,25 @@ Welcome to the **CrossPoint** firmware. This guide outlines the hardware control
       - [3.6.5 OPDS Servers (Multiple Libraries)](#365-opds-servers-multiple-libraries)
       - [3.6.6 Web Settings (Wi-Fi + OPDS)](#366-web-settings-wi-fi--opds)
       - [3.6.7 KOReader Sync Quick Setup](#367-koreader-sync-quick-setup)
+        - [Option A: Free Public Server (`sync.koreader.rocks`)](#option-a-free-public-server-synckoreaderrocks)
+        - [Option B: Self-Hosted Server (Docker Compose)](#option-b-self-hosted-server-docker-compose)
     - [3.7 Sleep Screen](#37-sleep-screen)
+      - [Cover settings](#cover-settings)
+      - [Custom images](#custom-images)
     - [3.8 Custom Fonts (SD Card)](#38-custom-fonts-sd-card)
   - [4. Reading Mode](#4-reading-mode)
-      - [Page Turning](#page-turning)
-      - [Chapter Navigation](#chapter-navigation)
-      - [Auto Page Turn](#auto-page-turn)
-      - [Tilt Page Turn (X3 only)](#tilt-page-turn-x3-only)
-      - [Footnote Navigation](#footnote-navigation)
-      - [System Navigation](#system-navigation)
-      - [Supported Languages](#supported-languages)
+    - [Page Turning](#page-turning)
+    - [Chapter Navigation](#chapter-navigation)
+    - [Auto Page Turn](#auto-page-turn)
+    - [Tilt Page Turn (X3 only)](#tilt-page-turn-x3-only)
+    - [Footnote Navigation](#footnote-navigation)
+    - [System Navigation](#system-navigation)
+    - [Supported Languages](#supported-languages)
   - [5. Reader Menu](#5-reader-menu)
-      - [5.1 Chapter Selection](#51-chapter-selection)
-      - [5.2 Bookmarks](#52-bookmarks)
-  - [6. Current Limitations & Roadmap](#6-current-limitations--roadmap)
-  - [7. Troubleshooting Issues & Escaping Bootloop](#7-troubleshooting-issues--escaping-bootloop)
+    - [5.1 Chapter Selection](#51-chapter-selection)
+    - [5.2 Bookmarks](#52-bookmarks)
+  - [6. Current Limitations \& Roadmap](#6-current-limitations--roadmap)
+  - [7. Troubleshooting Issues \& Escaping Bootloop](#7-troubleshooting-issues--escaping-bootloop)
 
 ## 1. Hardware Overview