[desktop] Data Manager, data import/export (#2700)

This adds a "Data Manager" dialog to the Tools menu. The Data Manager allows for the following operations:
- Open w/ system file manager
- Clear
- Export
- Import

On any of the following directories:
- Save (w/ profile selector)
- UserNAND
- SysNAND
- Mods
- Shaders

TODO for the future:
- "Cleanup" for each directory
- TitleID -> Game name--let users clean data for a specific game if applicable

Signed-off-by: crueter <crueter@eden-emu.dev>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/2700
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Reviewed-by: Lizzie <lizzie@eden-emu.dev>

src/frontend_common/data_manager.h

@@ -0,0 +1,24 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef DATA_MANAGER_H
+#define DATA_MANAGER_H
+
+#include "common/common_types.h"
+#include <string>
+
+namespace FrontendCommon::DataManager {
+
+enum class DataDir { Saves, UserNand, SysNand, Mods, Shaders };
+
+const std::string GetDataDir(DataDir dir, const std::string &user_id = "");
+
+u64 ClearDir(DataDir dir, const std::string &user_id = "");
+
+const std::string ReadableBytesSize(u64 size);
+
+u64 DataDirSize(DataDir dir);
+
+}; // namespace FrontendCommon::DataManager
+
+#endif // DATA_MANAGER_H