Bundle LZMA SDK for .edz extraction; drop 7z CLI dependency (M3)

Replaces the QProcess->7z shim with the public-domain LZMA SDK (23.01) 7-Zip
reader, vendored under sources/import/edz/lzma/ (decode-only subset). New
edzsevenzip.cpp wraps SzArEx_Open/SzArEx_Extract and writes entries via Qt, so
EdzArchive no longer needs an external 7-Zip at runtime. Enables the C language
in CMake for the vendored sources.

Verified: the bundled decoder extracts all three ifm sample .edz and the
generated elements still match the Python oracle exactly (byte-correct decode),
with no 7z on the path.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

sources/import/edz/lzma/SwapBytes.h

@@ -0,0 +1,17 @@
+/* SwapBytes.h -- Byte Swap conversion filter
+2023-04-02 : Igor Pavlov : Public domain */
+
+#ifndef ZIP7_INC_SWAP_BYTES_H
+#define ZIP7_INC_SWAP_BYTES_H
+
+#include "7zTypes.h"
+
+EXTERN_C_BEGIN
+
+void z7_SwapBytes2(UInt16 *data, size_t numItems);
+void z7_SwapBytes4(UInt32 *data, size_t numItems);
+void z7_SwapBytesPrepare(void);
+
+EXTERN_C_END
+
+#endif