Wipe token keyfile buffers on failure and release

Use a size_t counter in burn so large erasures retain their full length.
Install cleanup guards before token verification and keyfile application,
including the Windows token export path.

Reserve the complete EMV keyfile output before copying its components,
and wipe temporary components on every exit. Erase cached card data before
clearing or replacing it, including when copying a card fails.

Validation: Linux console and GUI builds with algorithm tests; cleanup
checks with GCC and Clang UBSan. PR 1816 still applies cleanly.

src/Volume/Keyfile.cpp

@@ -11,6 +11,7 @@
 */
 
 #include "Platform/Serializer.h"
+#include "Platform/Finally.h"
 #include "Common/SecurityToken.h"
 #include "Common/EMVToken.h"
 #include "Crc32.h"
@@ -36,6 +37,7 @@ namespace VeraCrypt
 		{
 			// Apply keyfile generated by a security token
 			vector <uint8> keyfileData;
+			finally_do_arg (vector <uint8> *, &keyfileData, { if (!finally_arg->empty()) burn (&finally_arg->front(), finally_arg->size()); });
 			Token::getTokenKeyfile(wstring(Path))->GetKeyfileData(keyfileData);
 
 			if (keyfileData.size() < MinProcessedLength)
@@ -57,8 +59,6 @@ namespace VeraCrypt
 					break;
 			}
 
-
-			burn(&keyfileData.front(), keyfileData.size());
 			goto  done;
 		}