fix: macOS deep links after wxWidgets 3.3.2 upgrade (#13737)

Fix macOS orcaslicer:// deep links after wxWidgets 3.3.2 upgrade

Install an OrcaSlicer-owned kAEGetURL Apple Event handler from
on_init_inner(). The wxWidgets 3.3.2 handler registered in
applicationWillFinishLaunching: stopped delivering URL events to
GUI_App::MacOpenURL on macOS (#13119), so links from Printables /
Thingiverse opened a blank project instead of importing the model.

Registering our own handler late in startup is last-writer-wins on
NSAppleEventManager and routes back to the existing MacOpenURL ->
start_download path, restoring the pre-upgrade behavior without
touching wxWidgets.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

src/slic3r/GUI/DeepLinkHandlerMac.h

@@ -0,0 +1,16 @@
+#ifndef slic3r_GUI_DeepLinkHandlerMac_h_
+#define slic3r_GUI_DeepLinkHandlerMac_h_
+
+namespace Slic3r {
+namespace GUI {
+
+// Re-registers a Cocoa Apple Event handler for kInternetEventClass/kAEGetURL.
+// Works around a regression observed after upgrading to wxWidgets 3.3.2 on
+// macOS Tahoe (#13119) where wxWidgets' built-in handler is registered but
+// never fires for orcaslicer:// deep links.
+void register_mac_deep_link_handler();
+
+} // namespace GUI
+} // namespace Slic3r
+
+#endif