Fix integer overflow in PSSH box KID count validation

[Copilot]

Addresses potential integer overflow in ParseProtectionSystemSpecificHeaderBox where kidCount * 16 multiplication could wrap around, bypassing bounds checks and causing buffer overruns with malformed MP4 files.

Changes:

• Add overflow validation before kidCount * 16 multiplication
• Include <cstdint> for SIZE_MAX constant
• Log error when overflow detected

uint32_t kidCount = ReadU32();
// Check for integer overflow before multiplication
if (kidCount > SIZE_MAX / 16)
{
    parseError = MP4_PARSE_ERROR_DATA_BOUNDARY_MISMATCH;
    MP4_LOG_ERR("Invalid KID count %u would cause integer overflow", kidCount);
    return;
}
size_t kidBytes = static_cast<size_t>(kidCount) * 16;

Without this check, a malicious kidCount value (e.g., SIZE_MAX / 16 + 1) would overflow to a small value, pass the subsequent bounds check at line 404, but advance ptr incorrectly at line 410.

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