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

tests/README.md

@@ -0,0 +1,55 @@
+# UI Test Files
+
+This directory contains JSON action playback tests for the Mosis Designer.
+
+## Running Tests
+
+```bash
+# From designer/build directory
+./Release/mosis-designer.exe --simulator --test-apps base-apps \
+    --playback ../../tests/test_settings.json \
+    --screenshot-after ../../tests/screenshots/result.png
+```
+
+## Test Files
+
+| File | Description |
+|------|-------------|
+| `test_home_only.json` | Wait and capture home screen |
+| `test_settings.json` | Navigate to Settings app |
+| `test_browser.json` | Navigate to Browser (dock) |
+| `test_messages.json` | Navigate to Messages app |
+| `test_messages_v2.json` | Messages with corrected coordinates |
+| `test_music.json` | Navigate to Music app |
+| `test_store.json` | Navigate to Mosis Store |
+| `test_navigation.json` | Multi-app navigation sequence |
+
+## Screenshots
+
+Captured screenshots are in `screenshots/`:
+- `screenshot_home_fresh.png` - Home screen
+- `screenshot_browser.png` - Browser app
+- `screenshot_messages_fixed.png` - Messages app
+- `screenshot_music_fixed.png` - Music app
+- `screenshot_settings_fixed.png` - Settings app
+- `screenshot_store_fixed.png` - Mosis Store
+
+## Hierarchy Dumps
+
+- `hierarchy_fresh.json` - Full UI element tree with bounds
+- `hierarchy_dump.json` - Previous hierarchy capture
+
+Use hierarchy dumps to find element coordinates for new tests.
+
+## Prerequisites
+
+Before running tests with `base-apps`, ensure shared assets exist at `MosisService/` root:
+
+```bash
+# Copy shared assets (run from MosisService/)
+cp -r src/main/assets/ui .
+cp -r src/main/assets/scripts .
+cp -r src/main/assets/icons .
+```
+
+See `docs/TESTING-FRAMEWORK.md` for full documentation.