test: add CTest, modular library structure, and Linux CI baseline

[daniyusk]

Summary

Prepares the repository for parallel development and automated testing without altering the functional scanner behavior.

Changes

• Adds .gitattributes to enforce LF endings across source files, build scripts, documentation, and configuration files.
• Separates CMake targets into JustGiveMyDisk::core (jgmd_core), jgmd_tui, and the JustGiveMyDisk executable.
• Enables CTest and adds minimal smoke tests (smoke.utf, smoke.parser, smoke.database) that run without initializing the TUI.
• Sets reproducible dependencies in cmake/Dependencies.cmake with pinned commit hashes for CLI11, fmt, FTXUI, and SHA256 verification for SQLite 3.50.4.
• Adds strict compiler warning configuration (-Wall -Wextra -Wpedantic -Wconversion -Wsign-conversion -Wshadow -Wformat=2 -Wundef) and addresses warning issues in Tui.cpp and MftRecord.cpp.
• Configures GitHub Actions CI workflow (.github/workflows/ci.yml) on Ubuntu with Debug and Release build matrix.

Commits

1. chore: normalize repository line endings
2. test: add CTest and Linux CI baseline

Verification

• Built all targets (jgmd_core, jgmd_tui, JustGiveMyDisk, jgmd_smoke_tests) with warnings treated as errors.
• Executed smoke tests via CTest (smoke.utf, smoke.parser, smoke.database), all passed.