Add histogram view transforms with ROI remap

[KedoKudo]

Summary

• add histogram view transforms with rotate/flip controls and status indication
• remap ROI shapes and overlays to keep selections aligned with transformed views
• update ROI spectra and cursor mapping to respect display transforms

Testing

• pixi run lint

Closes #116

[Copilot]

Pull request overview

This pull request implements histogram view transformations (rotate 90° CW/CCW, flip horizontal/vertical) with comprehensive ROI remapping to keep selections aligned with the transformed views. The implementation follows "Option A" from the linked issue #116, transforming ROI coordinates to stay visually attached to the same data regions.

Changes:

• Added ViewTransform state structure with rotation (0°/90°/180°/270°) and flip controls
• Implemented coordinate transformation functions for mapping between data and display space
• Updated ROI spectrum computation and cursor coordinate handling to respect transforms
• Added UI controls with keyboard shortcuts (R, Shift+R, H, V) and status indicators

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
rustpix-gui/src/state/ui.rs	Adds ViewTransform and Rotation types with coordinate transformation methods
rustpix-gui/src/state/mod.rs	Exports ViewTransform type
rustpix-gui/src/viewer/texture.rs	Renames function and adds transform parameter to apply coordinate mapping during image generation
rustpix-gui/src/viewer/roi.rs	Makes touch() method pub(crate) for external revision updates
rustpix-gui/src/viewer/mod.rs	Updates public API export
rustpix-gui/src/ui/main_view.rs	Adds transform control buttons, keyboard shortcuts, and applies transforms to hot pixel overlay and cursor mapping
rustpix-gui/src/ui/control_panel.rs	Updates status banner to show active transform state
rustpix-gui/src/app.rs	Implements ROI remapping logic, updates spectrum computation with transform awareness, and manages transform-sensitive cache invalidation

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