[FIX] install: bump Node.js to v22 for Capacitor v8 support

@capacitor/cli v8.x requires Node.js >=22.0.0. The install script
was pinning NODE_MAJOR=20, causing a fatal error when installing
the mobile app via todo.py.

--- FR ---

@capacitor/cli v8.x exige Node.js >= 22.0.0. Le script d'installation
figeait NODE_MAJOR=20, d'où une erreur fatale à l'installation de
l'application mobile depuis todo.py.

Assisted-by: Claude Sonnet 4.6

script/install/install_debian_dependency.sh

@@ -127,7 +127,8 @@ if [ "18.04" == "${UBUNTU_VERSION}" ]; then
   sudo apt remove nodeJS npm
   NODE_MAJOR=16
 else
-  NODE_MAJOR=20
+  # Node 22+ required by @capacitor/cli v8.x (mobile app dependency)
+  NODE_MAJOR=22
 fi
 
 echo "deb [signed-by=/etc/apt/keyrings/nodesource.gpg] https://deb.nodesource.com/node_$NODE_MAJOR.x nodistro main" | sudo tee /etc/apt/sources.list.d/nodesource.list