feat: qt5ct dark mode integration using ansible

ansible/playbooks/install_rviz_theme.yaml

@@ -0,0 +1,4 @@
+- name: Install RViz theme
+  hosts: localhost
+  roles:
+    - autoware.dev_env.qt5ct_setup

ansible/playbooks/universe.yaml

@@ -62,3 +62,6 @@
     # ONNX files and other artifacts
     - role: autoware.dev_env.artifacts
       when: prompt_download_artifacts == 'y'
+
+    # Qt5ct setup (RViz theme)
+    - role: autoware.dev_env.qt5ct_setup

ansible/roles/qt5ct_setup/README.md

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+# qt5ct_setup Ansible role
+
+## Overview
+
+The `qt5ct_setup` Ansible role automates the configuration of the `qt5ct` environment for Autoware.
+It won't affect the system-wide configuration.
+
+## Installation
+
+Follow the instructions below to **install** or **update** the custom theme for `RViz2` in Autoware.
+
+> **Important:** Both commands must be run when you want to update the theme.
+
+```bash
+cd ~/autoware # The root directory of the cloned repository
+ansible-galaxy collection install -f -r "ansible-galaxy-requirements.yaml"
+ansible-playbook autoware.dev_env.install_rviz_theme  --ask-become-pass
+```
+
+## How to use the custom theme in RViz2
+
+To apply a custom theme to RViz2, you can use the `qt5ct` platform theme. Follow these steps to ensure that the `QT_QPA_PLATFORMTHEME` environment variable is set correctly for your RViz2 instance when used with Autoware.
+
+### Manual setup for running RViz2
+
+Before running RViz2 manually, set the `QT_QPA_PLATFORMTHEME` environment variable to `qt5ct`.
+This ensures that the custom theme settings are applied.
+
+```bash
+export QT_QPA_PLATFORMTHEME=qt5ct
+```
+
+Then, start RViz2 as usual.
+
+```bash
+rviz2
+```
+
+### Automatic setup in Autoware
+
+In Autoware, the `QT_QPA_PLATFORMTHEME` environment variable is automatically set within the main [autoware.launch.xml](https://github.com/autowarefoundation/autoware_launch/blob/main/autoware_launch/launch/autoware.launch.xml) file.
+Therefore, you do not need to manually set this environment variable when launching Autoware.
+
+In the `autoware.launch.xml` file, RViz2 is configured with the following `<node>` element:
+
+```xml
+<node
+  pkg="rviz2"
+  exec="rviz2"
+  name="rviz2"
+  output="screen"
+  args="-d $(var rviz_config) -s $(find-pkg-share autoware_launch)/rviz/image/autoware.png"
+  if="$(var rviz)"
+  respawn="$(var rviz_respawn)">
+  <env name="QT_QPA_PLATFORMTHEME" value="qt5ct"/>
+</node>
+```
+
+This configuration automatically sets the `QT_QPA_PLATFORMTHEME` to `qt5ct` when RViz2 is launched as part of Autoware.
+It also includes additional options such as respawn behavior and custom RViz2 configurations.

ansible/roles/qt5ct_setup/defaults/main.yml

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+# defaults file for qt5ct_setup