SUSE-SU-2026:20030-1 Security update for libpng16

This update for libpng16 fixes the following issues: - CVE-2025-64505: heap buffer over-read in pngdoquantize when processing PNG files malformed palette indices bsc1254157. - CVE-2025-64506: heap buffer over-read in pngwriteimage8bit when processing 8-bit input with convertto8bit enabled...