Make bmp2epf buildable and runnable on Linux

[wren11]

Summary

• make bmp2epf compile with g++ on Linux by removing the Windows/GDI+ dependency from gdi_extract and delegating to the existing BMP parser
• replace invalid std::exception(message) usage with standard runtime/usage exceptions
• add missing standard/POSIX includes required by GCC and fix invalid width/height range checks

Validation

• g++ -std=c++17 -O2 -Wall -Wextra -pedantic *.cpp -o bmp2epf succeeds
• ./bmp2epf --help prints CLI usage
• generated a BMP fixture and converted it with ./bmp2epf --frame sample.bmp sample_output.epf, producing .epf, .pal, and .tbl outputs