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/com.mosis.settings/manifest.json

@@ -0,0 +1,16 @@
+{
+  "id": "com.mosis.settings",
+  "name": "Settings",
+  "version": "1.0.0",
+  "version_code": 1,
+  "entry": "settings.rml",
+  "icon": "/system/icons/settings.tga",
+  "description": "System settings and configuration",
+  "developer": {
+    "name": "Mosis Team",
+    "email": "dev@mosis.dev"
+  },
+  "is_system_app": true,
+  "permissions": [],
+  "min_api_version": 1
+}