Migrate data paths to ~/.local/share/fluorine/, add native build, fix %command% and system Proton scanning

- All data paths migrated from ~/.var/app/com.fluorine.manager/ to
  ~/.local/share/fluorine/ so native and Flatpak builds share the same
  instances, plugins, and configs
- New fluorinepaths.h/.cpp with fluorineDataDir() helper and one-time
  migration from old path (writes MOVED.txt breadcrumb)
- New libs/nak/src/paths.rs as Rust equivalent (data_dir())
- Strip %command% tokens from launch wrapper in protonlauncher.cpp
- Always scan /usr/share/steam/compatibilitytools.d/ for system Proton
  packages (Arch installs Proton there); add Flatpak filesystem permission
- Native build (build-native.sh) installs to ~/.local/share/fluorine/
  with desktop entry and ~/.local/bin symlink instead of portable zip
- build-flatpak.sh wrapper for Flatpak builds
- Fix container locale (LANG=C.UTF-8) for AutoUic warnings
- Fix prefixExists() to handle both compatdata and pfx directory layouts
- Fix globalInstancesRootPath() to use fluorineDataDir() on Linux
- Fix umu-run Flatpak lookup to use fluorineDataDir()
- Update README with build instructions and Arch dependency list

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

3 files changed, 12 insertions, 3 deletions

diff --git a/libs/game_bethesda/src/gamebryo/dummybsa.cpp b/libs/game_bethesda/src/gamebryo/dummybsa.cpp
index 7b0f877..3fbd2ef 100644
--- a/libs/game_bethesda/src/gamebryo/dummybsa.cpp
+++ b/libs/game_bethesda/src/gamebryo/dummybsa.cpp
@@ -19,6 +19,7 @@ along with Mod Organizer.  If not, see <http://www.gnu.org/licenses/>.
 
 #include "dummybsa.h"
 #include <QFile>
+#include <stdexcept>
 #ifdef _WIN32
 #define WIN32_LEAN_AND_MEAN
 #include <Windows.h>
@@ -184,7 +185,10 @@ void DummyBSA::writeFileRecordBlocks(QFile& file, const std::string& folderName)
 void DummyBSA::write(const QString& fileName)
 {
   QFile file(fileName);
-  file.open(QIODevice::WriteOnly);
+  if (!file.open(QIODevice::WriteOnly)) {
+    throw std::runtime_error(
+        QString("failed to open dummy BSA for writing: %1").arg(fileName).toStdString());
+  }
 
   m_TotalFileNameLength = static_cast<unsigned long>(m_FileName.length() + 1);
 
diff --git a/libs/game_bethesda/src/gamebryo/gamebryosavegame.cpp b/libs/game_bethesda/src/gamebryo/gamebryosavegame.cpp
index 523df0d..7625af3 100644
--- a/libs/game_bethesda/src/gamebryo/gamebryosavegame.cpp
+++ b/libs/game_bethesda/src/gamebryo/gamebryosavegame.cpp
@@ -9,6 +9,7 @@
 #include <QFileInfo>
 #include <QScopedArrayPointer>
 #include <QTime>
+#include <QTimeZone>
 
 #ifdef _WIN32
 #include <Windows.h>
@@ -90,7 +91,7 @@ void GamebryoSaveGame::setCreationTime(_SYSTEMTIME const& ctime)
   QTime time;
   time.setHMS(ctime.wHour, ctime.wMinute, ctime.wSecond, ctime.wMilliseconds);
 
-  m_CreationTime = QDateTime(date, time, Qt::UTC);
+  m_CreationTime = QDateTime(date, time, QTimeZone::UTC);
 }
 
 GamebryoSaveGame::FileWrapper::FileWrapper(QString const& filepath,
diff --git a/libs/game_bethesda/src/gamebryo/gamegamebryo.cpp b/libs/game_bethesda/src/gamebryo/gamegamebryo.cpp
index caeeed0..1bcc2c0 100644
--- a/libs/game_bethesda/src/gamebryo/gamegamebryo.cpp
+++ b/libs/game_bethesda/src/gamebryo/gamegamebryo.cpp
@@ -495,7 +495,11 @@ void GameGamebryo::copyToProfile(QString const& sourcePath,
     sourceFile = resolveFileCaseInsensitive(sourceFile);
     if (!MOBase::shellCopy(sourceFile, filePath)) {
       // if copy file fails, create the file empty
-      QFile(filePath).open(QIODevice::WriteOnly);
+      QFile outputFile(filePath);
+      if (!outputFile.open(QIODevice::WriteOnly)) {
+        MOBase::log::warn("Failed to create fallback file '{}': {}", filePath,
+                          outputFile.errorString());
+      }
     }
   }
 }