FRE-606: Add icon generation and tests for Tauri desktop

- Add generate-icons.sh script for cross-platform icon generation
- Generate all required icon sizes (32x32, 128x128, 256x256, 512x512)
- Create Windows .ico and macOS .icns icons
- Add Rust unit tests for core functionality
- Add tauri:test and tauri:icons npm scripts

New files:
- src-tauri/generate-icons.sh
- src-tauri/icons/32x32.png
- src-tauri/icons/128x128.png
- src-tauri/icons/128x128@2x.png
- src-tauri/icons/512x512.png
- src-tauri/icons/icon.ico
- src-tauri/icons/icon.icns
- src-tauri/icons/src/app-icon.svg
- src-tauri/icons/tray-icon.png
- src-tauri/src/tests.rs

Modified:
- src-tauri/src/lib.rs (added tests module)

src-tauri/src/lib.rs

@@ -1,6 +1,8 @@
 pub mod menu;
 pub mod tray;
 pub mod updater;
+#[cfg(test)]
+pub mod tests;
 
 use serde::{Deserialize, Serialize};
 

src-tauri/src/tests.rs

@@ -0,0 +1,52 @@
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_greet_command() {
+        let result = greet("World");
+        assert_eq!(result, "Hello, World! You've been greeted from Rust!");
+    }
+
+    #[test]
+    fn test_app_state_default() {
+        let state = AppState::default();
+        assert!(!state.app_version.is_empty());
+        assert_eq!(state.is_dev_mode, cfg!(debug_assertions));
+    }
+
+    #[test]
+    fn test_window_state_serialization() {
+        let state = WindowState {
+            width: 1280.0,
+            height: 800.0,
+            x: 100,
+            y: 100,
+            is_maximized: false,
+        };
+
+        let serialized = serde_json::to_string(&state).unwrap();
+        let deserialized: WindowState = serde_json::from_str(&serialized).unwrap();
+
+        assert_eq!(state.width, deserialized.width);
+        assert_eq!(state.height, deserialized.height);
+        assert_eq!(state.x, deserialized.x);
+        assert_eq!(state.y, deserialized.y);
+        assert_eq!(state.is_maximized, deserialized.is_maximized);
+    }
+
+    #[test]
+    fn test_update_info_serialization() {
+        let update_info = UpdateInfo {
+            current_version: "0.1.0".to_string(),
+            latest_version: "0.2.0".to_string(),
+            release_notes: "Bug fixes".to_string(),
+            download_url: "https://example.com/update".to_string(),
+            is_update_available: true,
+        };
+
+        let serialized = serde_json::to_string(&update_info).unwrap();
+        assert!(serialized.contains("0.2.0"));
+        assert!(serialized.contains("Bug fixes"));
+    }
+}