⚡ Bolt: Optimize file reading performance

[Jayian1890]

⚡ Bolt: Optimize file reading performance

Replace stringstream-based file reading with direct string construction from stream iterators to eliminate intermediate buffering overhead.

💡 What: Changed read_file() to use std::string(std::istreambuf_iterator<char>(file), {}) instead of stringstream
🎯 Why: Removes stringstream overhead for better performance when reading files
📊 Impact: Small improvement in file reading performance, especially for larger files
🔬 Measurement: Verified with existing tests - all 138 test cases pass

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.63%. Comparing base (fac2486) to head (d39a207).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #27      +/-   ##
==========================================
- Coverage   89.64%   89.63%   -0.01%     
==========================================
  Files           8        8              
  Lines        3669     3667       -2     
  Branches      349      349              
==========================================
- Hits         3289     3287       -2     
  Misses        380      380              

Flag	Coverage Δ
unitests	89.63% <100.00%> (-0.01%)	⬇️

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