Add Adjustments, Watermark, Rename wizard steps; expand to 10-step wizard

- New step_adjustments: rotation (5 options) and flip (3 options)
- New step_watermark: text/image watermark with position, opacity, font size
- New step_rename: prefix/suffix/counter with live preview and template engine
- Updated step_metadata: added Custom mode with per-category checkboxes
  (GPS, camera, software, timestamps, copyright) with show/hide toggle
- Expanded JobConfig with all operation fields (watermark, rename, metadata custom)
- Updated wizard from 7 to 10 steps in correct pipeline order
- Fixed page index references from 6 to 9 for output step
- Added MetadataMode::Custom handling in preset builder and output summary

pixstrip-gtk/src/steps/mod.rs

@@ -1,7 +1,10 @@
+pub mod step_adjustments;
 pub mod step_compress;
 pub mod step_convert;
 pub mod step_images;
 pub mod step_metadata;
 pub mod step_output;
+pub mod step_rename;
 pub mod step_resize;
+pub mod step_watermark;
 pub mod step_workflow;