Fix speed settings initialization and add config file documentation

- Fix speed toggle not reading saved turboMode setting from QSettings
- Speed toggle now properly reflects saved state instead of defaulting to false
- Ensures correct defaults: 1x speed with turbo mode unchecked
- Improve Windows/Linux audio stability with larger buffers
- Add Configuration Files section to README documenting storage locations
  for all platforms (macOS, Windows, Linux)

Including debug messages for ROM loading procedure

Disable 80-column display support pending proper implementation

This change temporarily disables all 80-column display hardware options and the main 80-column display setting in the UI to prevent user confusion and potential issues:

- Disabled XEP80, Austin Franklin 80, Bit3 Full View 80, and Proto 80-Column hardware options
- Disabled the main "Enable 80-Column Display" video setting
- All affected checkboxes are now unchecked and grayed out with tooltips explaining they need more work
- Settings are forced to false in save/load operations to ensure consistent state
- Updated CLAUDE.md with build script version requirements and build error handling notes

The 80-column display functionality requires additional implementation work to function correctly. These options will be re-enabled once the underlying support is properly implemented and tested.

Implement centralized version management

- Create version.h.in template for CMake configuration
- Generate version.h at build time with version info
- Update mainwindow.cpp to use version from header
- Link --version parameter in build.sh to CMake PROJECT_VERSION
- Window title and About dialog now show correct version
- Version can be overridden: ./build.sh --version v1.0.2
- Automatically includes build date and git commit hash

This ensures version consistency across:
- Build artifacts (DMG/ZIP filenames)
- Application UI (window title, about dialog)
- Bundle metadata (Info.plist)

Fix debugger step_over to use instruction-level stepping

- Changed step_over implementation from using breakpoints and full emulation
  to instruction-level stepping for precise control
- Both DebuggerWidget and TCP server now use the same stepping approach
- Step_over now properly executes JSR and steps through subroutine until return
- Added debugStepped signal for UI synchronization
- Connected DebuggerWidget to AtariEmulator signals for real-time updates
- Fixed synchronization between TCP commands and debug widget display
- Safety limit of 10,000 instructions prevents infinite loops in subroutines
- Added documentation for debug.step_into and debug.step_over TCP commands

This fixes the issue where step_over was using coarse frame-level stepping
and ensures consistent behavior between UI and TCP debugging interfaces.

Fix disk LED activity and cross-platform build issues

- Add missing extern declaration for libatari800_set_disk_activity_callback
- Disable SDL2 for Windows and Linux builds (container environments)
- Disable SDL2 for macOS x86_64 builds (typically not installed)
- Create comprehensive build checklist to prevent regression
- Ensure patches are properly applied across all platforms

SDL2 is now only enabled for macOS ARM64 builds where it's reliably available.
All other platforms use Qt audio backend for consistency.