This commit completes Phase 2 of the benviplot 1.0.0 release plan,
modernizing the codebase and ensuring clean R CMD check results.

## Critical Bug Fixes
- Fixed plot_line_trend(): size → linewidth for ggplot2 4.0.0
- Fixed plot_line_trend(): return value assignment bug
- Fixed plot_column_label(): guide_fill → fill_guide typo
- Fixed plot_column_label(): label aesthetic tidy evaluation
- Fixed plot_area(): label → labels in scale call
- Fixed plot_column(): T → TRUE

## Breaking Changes
- BREAKING: Renamed 'pal' → 'palette' in all plot functions

## Error Handling Modernization
- Replaced stop() with cli::cli_abort() in benvi_palette.R
- Replaced stop() with cli::cli_abort() in benvi_scales.R
- Replaced stopifnot() with cli::cli_abort() in plot functions
- Added input validation to pretty_number()
- Enhanced import_fonts() with robust error handling

## Code Quality
- Refactored plot_add_xy() using switch()
- Refactored get_hist_bw() using switch(), fixed = → <-
- Implemented .onLoad()/.onAttach() pattern per R best practices

## Documentation
- Added data-masking tags to all tidy eval parameters
- Updated RoxygenNote: 7.3.2 → 7.3.3
- Added missing imports (guides)

## R CMD Check Fixes
- Fixed global variable bindings (R/utils-globals.R)
- Removed unused rlang dependency
- Updated .Rbuildignore for build artifacts
- VERIFIED: 0 errors, 0 warnings, 0 notes ✓

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Co-Authored-By: Claude <noreply@anthropic.com>