Wire tiled, margin, and scale UI controls to JobConfig and pass
through to WatermarkConfig. Add tiled text and image watermark
implementations that repeat across the full image. Add font family
filesystem search for named fonts. Add WatermarkRotation enum.
Font picker using GTK FontDialog/FontDialogButton lets users choose
any installed system font for text watermarks. The selected font family
is passed through the processing pipeline and used to find the matching
font file on disk.
Support resize algorithm selection (lanczos3/catmullrom/bilinear/nearest)
and overwrite behavior (auto-rename/overwrite/skip) in the CLI process
command, matching the GUI functionality.
Process command discovers images, builds pipeline from preset or CLI
flags (--resize, --format, --quality, --strip-metadata, --recursive),
executes with progress output, prints results with size savings, and
saves to history. Preset list/export/import use the storage module.
