refactor: extract theme from ztools into base distribution (#278)

- Add Spreadsheet color preferences to KindredCreate.cfg using FCText
  entries (TextColor, AliasedCellBackgroundColor, PositiveNumberColor,
  NegativeNumberColor) matching the C++ GetASCII() reader in SheetModel.cpp
- Remove CatppuccinMocha install directive from CMakeLists.txt
- Update ztools submodule: theme.py deleted, CatppuccinMocha preference
  pack removed, package.xml cleaned up

The previous apply_spreadsheet_colors() in ztools was a no-op: it called
SetUnsigned() but the Spreadsheet C++ reads GetASCII() — different param
types in FreeCAD's parameter system. Now properly fixed via preference pack.

Closes #278

src/Mod/Create/CMakeLists.txt

@@ -48,12 +48,6 @@ install(
     DESTINATION
         mods/ztools
 )
-install(
-    DIRECTORY
-        ${CMAKE_SOURCE_DIR}/mods/ztools/CatppuccinMocha
-    DESTINATION
-        mods/ztools
-)
 install(
     FILES
         ${CMAKE_SOURCE_DIR}/mods/ztools/package.xml