Route startup storage paths through platform services

src/platform_api/platform_services.h

@@ -10,10 +10,18 @@ namespace pp::platform {
 using PickedPathCallback = std::function<void(std::string path)>;
 using PreparedFileCallback = std::function<void(std::string path, bool saved)>;
 
+struct PlatformStoragePaths {
+    std::string data_path;
+    std::string work_path;
+    std::string recording_path;
+    std::string temporary_path;
+};
+
 class PlatformServices {
 public:
     virtual ~PlatformServices() = default;
 
+    [[nodiscard]] virtual PlatformStoragePaths prepare_storage_paths() = 0;
     [[nodiscard]] virtual std::string clipboard_text() = 0;
     [[nodiscard]] virtual bool set_clipboard_text(std::string_view text) = 0;
     virtual void set_cursor_visible(bool visible) = 0;