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.sandbox-test/styles.rcss

@@ -0,0 +1,97 @@
+body {
+    font-family: LatoLatin;
+    font-size: 16dp;
+    background-color: #121212;
+    color: #ffffff;
+    width: 100%;
+    height: 100%;
+}
+
+.app-bar {
+    display: flex;
+    flex-direction: row;
+    align-items: center;
+    height: 56dp;
+    background-color: #1e1e1e;
+    padding: 0 8dp;
+}
+
+.app-bar-nav {
+    width: 40dp;
+    height: 40dp;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    border-radius: 20dp;
+}
+
+.app-bar-nav:hover {
+    background-color: #333333;
+}
+
+.icon {
+    font-size: 24dp;
+}
+
+.app-bar-title {
+    font-size: 20dp;
+    font-weight: bold;
+    margin-left: 16dp;
+}
+
+.content {
+    display: block;
+    padding: 16dp;
+    width: auto;
+    box-sizing: border-box;
+}
+
+.card {
+    display: block;
+    background-color: #1e1e1e;
+    border-radius: 12dp;
+    padding: 16dp;
+    margin-bottom: 12dp;
+}
+
+.card-title {
+    display: block;
+    font-size: 18dp;
+    font-weight: bold;
+    margin-bottom: 8dp;
+    color: #bb86fc;
+}
+
+.card div {
+    display: block;
+}
+
+button {
+    display: block;
+    background-color: #bb86fc;
+    color: #000000;
+    border-width: 0;
+    border-radius: 8dp;
+    padding: 12dp 24dp;
+    font-size: 14dp;
+    font-weight: bold;
+    margin-top: 8dp;
+}
+
+button:hover {
+    background-color: #cf9fff;
+}
+
+button:active {
+    background-color: #9a67ea;
+}
+
+#results {
+    font-family: LatoLatin;
+    font-size: 12dp;
+    background-color: #0d0d0d;
+    padding: 12dp;
+    border-radius: 8dp;
+    white-space: pre-wrap;
+    color: #00ff00;
+}