Linux: add emergency cleanup for stale unmounts

When normal filesystem unmount fails, the Linux path could stop before cleaning VeraCrypt mapper, loop and FUSE objects. Add an explicit emergency dismount request that is only reached after interactive confirmation.

The recovery path lazy-detaches mounted filesystems, uses deferred dmsetup removal for VeraCrypt mapper devices, detaches loop devices, and keeps normal force/ignoreOpenFiles behavior unchanged.

src/Main/Forms/WaitDialog.cpp

@@ -66,6 +66,7 @@ namespace VeraCrypt
 		VC_CONVERT_EXCEPTION (MissingArgument);
 		VC_CONVERT_EXCEPTION (NoItemSelected);
 		VC_CONVERT_EXCEPTION (StringFormatterException);
+		VC_CONVERT_EXCEPTION (FilesystemDismountFailed);
 		VC_CONVERT_EXCEPTION (ExecutedProcessFailed);
 		VC_CONVERT_EXCEPTION (AlreadyInitialized);
 		VC_CONVERT_EXCEPTION (AssertionFailed);