feat: Improve thermal display and build system

- Replace emoji thermal indicators with modern progress bar UI
- Switch temperature source to battery sensor for better accuracy
- Adjust temperature thresholds (30°C-45°C range)
- Add automatic Vulkan Validation Layer download for Android
- Downgrade Java/Kotlin target to 17 for wider compatibility

The thermal display now shows a visual progress bar with percentage
instead of emojis, making it easier to gauge system temperature at
a glance. Temperature reading now comes from the battery sensor
which is more reliable across devices.

Build system improvements include automated VVL binary downloads
and installation for Android builds when CITRON_DOWNLOAD_ANDROID_VVL
is enabled. Java target downgraded to 17 to ensure compatibility
with current Android toolchain.

CMakeLists.txt

@@ -97,7 +97,26 @@ if (ANDROID OR WIN32 OR APPLE)
 endif()
 option(ENABLE_OPENSSL "Enable OpenSSL backend for ISslConnection" ${DEFAULT_ENABLE_OPENSSL})
 
-# Copy the VVL arm64 binary to src/android/app/main/jniLibs. REF: https://github.com/KhronosGroup/Vulkan-ValidationLayers/actions/workflows/vvl.yml
+if (ANDROID AND CITRON_DOWNLOAD_ANDROID_VVL)
+    set(vvl_version "sdk-1.3.261.1")
+    set(vvl_zip_file "${CMAKE_BINARY_DIR}/externals/vvl-android.zip")
+    if (NOT EXISTS "${vvl_zip_file}")
+        # Download and extract validation layer release to externals directory
+        set(vvl_base_url "https://github.com/KhronosGroup/Vulkan-ValidationLayers/releases/download")
+        file(DOWNLOAD "${vvl_base_url}/${vvl_version}/android-binaries-${vvl_version}-android.zip"
+            "${vvl_zip_file}" SHOW_PROGRESS)
+        execute_process(COMMAND ${CMAKE_COMMAND} -E tar xf "${vvl_zip_file}"
+                        WORKING_DIRECTORY "${CMAKE_BINARY_DIR}/externals")
+    endif()
+
+    # Copy the arm64 binary to src/android/app/main/jniLibs only if it doesn't exist
+    set(vvl_lib_path "${CMAKE_CURRENT_SOURCE_DIR}/src/android/app/src/main/jniLibs/arm64-v8a/")
+    set(vvl_lib_file "${vvl_lib_path}/libVkLayer_khronos_validation.so")
+    if (NOT EXISTS "${vvl_lib_file}")
+        file(COPY "${CMAKE_BINARY_DIR}/externals/android-binaries-${vvl_version}/arm64-v8a/libVkLayer_khronos_validation.so"
+                DESTINATION "${vvl_lib_path}")
+    endif()
+endif()
 
 if (ANDROID)
     set(CMAKE_SKIP_INSTALL_RULES ON)