[pro-laxmi]

Summary

Standard C library <ctype.h> functions (isblank, tolower, toupper, isalpha, etc.) require their argument to be representable as an unsigned char or equal to EOF. Passing a signed char with a negative value (such as non-ASCII UTF-8 bytes $\ge 0x80$) invokes undefined behavior and can cause out-of-bounds array indexing in libc lookup tables.

This PR audits and casts char to (unsigned char) across remaining call sites:

• src/common/impl/FFstrbuf.c: ffStrbufUpperCase and ffStrbufLowerCase
• src/modules/media/media.c: shouldIgnoreChar and artistInSongTitle
• src/common/impl/font.c: ffFontInitQt
• src/common/impl/properties.c: ffParsePropLinePointer
• src/detection/chassis/chassis_linux.c: ffDetectChassis
• src/detection/cpu/cpu_linux.c: detectAndroid and detectPhysicalCores
• src/modules/packages/packages.c: ffParsePackagesJsonObject
• src/modules/player/player.c: ffPrintPlayer
• src/logo/logo.c: logoGetBuiltin
• src/detection/wm/wm_apple.m: ffDetectWMPlugin
• src/detection/wmtheme/wmtheme_windows.c: ffDetectWmTheme

Testing

• Added test coverage in tests/strbuf.c verifying ffStrbufUpperCase and ffStrbufLowerCase with non-ASCII bytes (\x80, \xff).
• All 20 tests pass cleanly (ctest --output-on-failure).