CLSA-2026-1777311274 Fix CVE(s): CVE-2026-22801, CVE-2026-25646

SECURITY UPDATE: Heap buffer over-read in pngwriteimage due to truncation of ptrdifft row stride to pnguint16 - debian/patches/CVE-2026-22801.patch: remove incorrect truncation casts from pngwriteimage16bit, pngwriteimage8bit, and pngimagewritemain so large 65535 and negative row strides are...