test: Add Compose screenshot testing support

Integrate the experimental Android screenshot testing plugin into the `core:ui` module. This includes initial visual regression tests for Alert components and updates to the CI workflow for automated validation.

- core/ui: Add `AlertScreenshotTest` and screenshot test dependencies
- gradle.properties: Enable `android.experimental.enableScreenshotTest`
- libs.versions.toml: Add `com.android.compose.screenshot` plugin and validation API
- reusable-check.yml: Add screenshot validation tasks to GitHub Actions workflow

.github/workflows/reusable-check.yml

@@ -12,6 +12,9 @@ on:
       run_instrumented_tests:
         type: boolean
         default: true
+      run_screenshot_tests:
+        type: boolean
+        default: true
       flavors:
         type: string
         default: '["google"]'
@@ -110,6 +113,15 @@ jobs:
             fi
           fi
           
+          # Screenshot Test Tasks
+          if [ "${{ inputs.run_screenshot_tests }}" = "true" ] && [ "$IS_FIRST_API" = "true" ]; then
+            if [ "$FLAVOR" = "google" ]; then
+              TASKS="$TASKS validateGoogleDebugScreenshotTest "
+            elif [ "$FLAVOR" = "fdroid" ]; then
+              TASKS="$TASKS validateFdroidDebugScreenshotTest "
+            fi
+          fi
+          
           # Instrumented Test Tasks
           if [ "${{ inputs.run_instrumented_tests }}" = "true" ]; then
             [ "$IS_FIRST_FLAVOR" = "true" ] && TASKS="$TASKS connectedDebugAndroidTest "