IIS: fix Content-Length formatting (correct printf specifier + full buffer size)

[A13501350]

Summary

Fixes the Content-Length header value being corrupted/truncated in the IIS module when ModSecurity has to synthesize it (only-response, non-chunked case).

Two defects were fixed in iis/mymodule.cpp:

• ulTotalLength is a ULONGLONG, but was printed with "%d" (32-bit int). printf only consumed the low 32 bits, producing a wrong header for response bodies larger than ~2 GiB. Now uses "%llu".
• The two other call sites format an unsigned int length with "%d"; changed to "%u".
• StringCchPrintfA's cchDest was passed as sizeof(szLength)/sizeof(CHAR) - 1 (20), which can only hold 19 digits + null and would truncate a 20-digit 64-bit value. Now passes the full buffer size (21, which includes the null terminator).

Fixes

Closes #3619

Changed locations

• iis/mymodule.cpp:644 — ulTotalLength (ULONGLONG) -> "%llu"
• iis/mymodule.cpp:1142 — length (unsigned int) -> "%u"
• iis/mymodule.cpp:1230 — length (unsigned int) -> "%u"

All three now pass sizeof(szLength) / sizeof(CHAR) as the destination size.

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[sonarqubecloud]

Quality Gate failed

Failed conditions
C Maintainability Rating on New Code (required ≥ A)

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