Refactor librarybuilder, fix bugs, security, build system, and tests

[zjshermanburke]

Summary

• Fix SQL injection, memory leaks, no-op delete_row, and Book.cpp set_sub_genre bug
• Replace hardcoded database credentials with environment variables
• Improve code quality: const references, Rule of Five, return by const reference
• Add CMakeLists.txt build system with Google Test framework and coverage support
• Add CI workflow for automated build and unit tests
• Revert to exec_params for libpqxx compatibility with CI runner

Bugs Fixed

• SQL injection → parameterized queries (exec_params)
• Memory leaks in load_movie_collection/load_book_collection → stack variables
• No-op delete_row → executes the query
• Book.cpp set_sub_genre → assigns correct member

Security

• Hardcoded credentials → environment variables via std::getenv

Code Quality

• Pass-by-value strings → const std::string &
• Getters return by const reference
• Rule of Five for MovieCollection and BookCollection
• Consistent & style (name-attached)

Build System

• CMakeLists.txt with separate main and test executables
• Test coverage support via lcov
• Google Test framework with unit and integration tests
• GitHub Actions CI workflow

Cleanup

• Comments corrected (movie → book where appropriate)
• Test includes removed from main.cpp
• Table name validation helper