Add system update guide for M4N-Dock and M4N-Hat; update sidebar links

- Created a new document for the system update guide specific to M4N-Dock and M4N-Hat in the `m4n_c-SoM` directory.
- Updated sidebar links to reflect the new file structure and ensure correct navigation for M4N and M4N-Dock/M4N-Hat sections.

docs/hardware/en/maixIV/m4n/system-update.md

@@ -1,4 +1,4 @@
-This guide provides detailed instructions for two system flashing methods for the M4N-Dock development board:
+This guide provides detailed instructions for two system flashing methods for the M4N development board series:
 
 1. booting and flashing eMMC via TFCard
 2. flashing using the AXDL tool
@@ -8,7 +8,7 @@ Please choose the appropriate method based on your needs.
 
 ## Image File
 
-*Due to the large size of the image packages used in the flashing methods described on this page and limited bandwidth on the download site, they are stored exclusively on Baidu Enterprise Drive in the same directory. The entry link can be found in the [top side of the download site](https://dl.sipeed.com/)。*
+*Due to the large size of the image packages used in the flashing methods described on this page and limited bandwidth on the download site, they are stored exclusively on Mega Drive in the same directory. The entry link can be found in the [top side of the download site](https://dl.sipeed.com/)。*
 
 
 | Image Type        | How to Boot                               | Filename     | How to Obtain     |

docs/hardware/zh/sidebar.yaml

@@ -111,31 +111,30 @@ items:
             file: maixIII/ax-pi/faq_axpi.md
 -   label: Maix-IV
     items:
-    -   label: Maix M4N
-    #     file: maixIV/m4n/m4n.md
+    -   label: M4N & M4C SoM
         items:
         -   label: 系统烧录指南
-            file: maixIV/m4n/system-update.md
+            file: maixIV/m4n_c-SoM/system-update.md
         -   label: AI 模型部署
-            file: maixIV/m4n/axmodel-deploy.md
+            file: maixIV/m4n_c-SoM/axmodel-deploy.md
         -   label: FAQ
-            file: maixIV/m4n/FAQ.md
-    -   label: Maix M4N-Dock
+            file: maixIV/m4n_c-SoM/FAQ.md
+    -   label: M4 Dock Carrier Board
         items:
         -   label: 产品介绍
             file: maixIV/m4ndock/intro.md
         -   label: 系统烧录指南
-            file: maixIV/m4n/system-update.md
+            file: maixIV/m4n_c-SoM/system-update.md
         -   label: 产品上手指南
             file: maixIV/m4ndock/quick-start.md
         -   label: FAQ
             file: maixIV/m4ndock/FAQ.md
-    -   label: Maix M4N-Hat
+    -   label: M4 Hat Carrier Board
         items:
         -   label: 产品介绍
             file: maixIV/m4nhat/intro.md
         -   label: 系统烧录指南
-            file: maixIV/m4n/system-update.md
+            file: maixIV/m4n_c-SoM/system-update.md
         -   label: 产品上手指南
             file: maixIV/m4nhat/quick-start.md
         -   label: 树莓派5 PCIe 加速指南