add base-apps with manifests, layout system, and testing documentation

- Rename test-apps to base-apps with proper manifest.json for each app
- Add is_system_app flag to app discovery and Lua API
- Fix icon path resolution for /system/icons/ paths
- Add layout.lua and layout.rcss for reusable UI components
- Update home screen to dynamically load all apps from manifests
- Update all app RML files to use layout components
- Comprehensive testing framework documentation with JSON action format
- Add tests/ directory structure for automated UI testing

base-apps/package.bat

@@ -0,0 +1,21 @@
+@echo off
+REM Package test apps as .mosis files
+
+setlocal enabledelayedexpansion
+
+for /d %%d in (*) do (
+    if exist "%%d\manifest.json" (
+        echo Packaging %%d...
+        cd %%d
+        if exist "..\%%d.mosis" del "..\%%d.mosis"
+        tar -a -cf "..\%%d.mosis" *
+        cd ..
+        echo Created %%d.mosis
+    )
+)
+
+echo.
+echo Done! Package files:
+dir /b *.mosis 2>nul
+
+endlocal