Fix type conversion warnings in base58.cpp and improve CMake syntax

CMakeLists.txt

@@ -112,12 +112,11 @@ if(ENABLE_LLVM_COVERAGE)
     add_compile_options(-fprofile-instr-generate -fcoverage-mapping)
     add_link_options(-fprofile-instr-generate)
 
-    # Helper variables for report tools (can be overridden from environment)
+    # Helper variables for report tools
     set(LLVM_PROFDATA "llvm-profdata" CACHE STRING "Path to llvm-profdata")
     set(LLVM_COV "llvm-cov" CACHE STRING "Path to llvm-cov")
 
     # Custom target to run tests and produce coverage report
-    # Usage: cmake --build build --target coverage_llvm --config Release
     add_custom_target(
         coverage_llvm
         COMMAND ${CMAKE_COMMAND} -E env