feat: custom scrollbars, portable storage, window state persistence

- Custom scrollbar CSS using ::-webkit-scrollbar for Tauri's Chromium WebView
- Portable storage: all data written next to exe in data/ folder instead of AppData
- Rust get_portable_data_dir command with runtime FS scope for exe directory
- Window size/position/maximized saved to settings on close, restored on startup

src-tauri/src/lib.rs

@@ -1,3 +1,15 @@
+use tauri_plugin_fs::FsExt;
+
+#[tauri::command]
+fn get_portable_data_dir() -> Result<String, String> {
+    let exe_path = std::env::current_exe().map_err(|e| e.to_string())?;
+    let exe_dir = exe_path
+        .parent()
+        .ok_or_else(|| "Failed to get exe directory".to_string())?;
+    let data_dir = exe_dir.join("data");
+    Ok(data_dir.to_string_lossy().to_string())
+}
+
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
     tauri::Builder::default()
@@ -5,6 +17,27 @@ pub fn run() {
         .plugin(tauri_plugin_fs::init())
         .plugin(tauri_plugin_dialog::init())
         .plugin(tauri_plugin_shell::init())
+        .setup(|app| {
+            // Get portable data directory next to the exe
+            let exe_path =
+                std::env::current_exe().expect("Failed to get exe path");
+            let exe_dir = exe_path
+                .parent()
+                .expect("Failed to get exe directory");
+            let data_dir = exe_dir.join("data");
+
+            // Ensure data directory exists
+            std::fs::create_dir_all(&data_dir)
+                .expect("Failed to create portable data directory");
+
+            // Allow FS plugin access to the portable data directory
+            app.fs_scope()
+                .allow_directory(&data_dir, true)
+                .expect("Failed to allow data directory in FS scope");
+
+            Ok(())
+        })
+        .invoke_handler(tauri::generate_handler![get_portable_data_dir])
         .run(tauri::generate_context!())
         .expect("error while running tauri application");
 }