feat(travel): Implement settings UI and web server for MTR route configuration

- Added MainUIHandler class to manage the main UI and polling for arrival data.
- Introduced SettingsUI class for displaying QR code and configuration options.
- Created SettingsUIHandler to manage settings UI lifecycle and web server interactions.
- Developed WebHandler to handle HTTP requests for MTR route settings, including adding and removing routes.
- Implemented web endpoints for fetching MTR lines, routes, and saving settings.
- Enhanced UI with responsive design for e-ink displays and added error handling for web interactions.

main/ui/apps/CMakeLists.txt

@@ -1,7 +1,7 @@
 # Control which apps are included in the build.
 # Override `ENABLED_APPS` from the top-level CMake command line to change apps.
 if(NOT DEFINED ENABLED_APPS)
-    set(ENABLED_APPS "iotdis")
+    set(ENABLED_APPS "iotdis" "travel")
     endif()
 message(STATUS "Enabled apps: ${ENABLED_APPS}")