fix(startup): prevent main thread hangs and optimize resource loading

- run start_sh initialization via QTimer.singleShot with timeout
- add timeout protection to load_theme_fonts()
- load Steam/EGS/PortProton games in parallel instead of sequential
- delay game loading until UI is fully initialized
- fix callback chaining to avoid blocking operations
- add proper timeout + error handling for all Steam/EGS network requests
- add timeouts for flatpak subprocess calls
- improve file I/O error handling to avoid UI freeze
- optimize theme font loading:
  - delay font loading via QTimer.singleShot
  - load fonts in batches of 10
  - reduce font load timeout to 3s
  - remove fonts only when switching themes

Signed-off-by: Boris Yumankulov <boria138@altlinux.org>

portprotonqt/input_manager.py

@@ -159,7 +159,8 @@ class InputManager(QObject):
         logger.info("EMUL: Mouse emulation initialized (enabled=%s)", self.mouse_emulation_enabled)
 
         if self.mouse_emulation_enabled:
-            self.enable_mouse_emulation()
+            # Initialize mouse emulation asynchronously to avoid blocking startup
+            QTimer.singleShot(0, self._async_enable_mouse_emulation)
 
         # FileExplorer specific attributes
         self.file_explorer = None
@@ -197,6 +198,10 @@ class InputManager(QObject):
         # Initialize evdev + hotplug
         self.init_gamepad()
 
+    def _async_enable_mouse_emulation(self):
+        """Asynchronously enable mouse emulation to avoid blocking startup."""
+        self.enable_mouse_emulation()
+
     def _update_emulation_flag(self):
         """Update emulation_active flag based on Qt app focus (main thread only)."""
         active = QApplication.activeWindow()