Fix CRAN-blocking issues for package submission

[Arshammik]

This commit addresses critical issues that would prevent CRAN acceptance:

1. Remove .onLoad auto-install (CRAN policy violation)

   • Removed automatic package installation from R/zzz.R
   • Dependencies should only be declared in DESCRIPTION file

2. Fix Makevars.linux portability

   • Removed -march=native flag that causes binary incompatibility
   • Binaries will now work across different CPU architectures

3. Fix thread safety issues in C++ code

   • Converted static bool to std::atomic in deviance_gene.cpp
   • Converted static bool to std::atomic in calcDeviances.cpp
   • Used compare_exchange_strong for thread-safe one-time printing

4. Clean up code quality issues

   • Fixed typos in R/feature_selection.R comments
   • Removed unreachable code after return statement
   • Fixed typo