V94 USGS-STYLE FINITE-FAULT EXPORT

Base
- Built from the stable v90 branch as requested.

What changed
- Adds an export feature for directly input finite-fault stamp patches.
- Press Ctrl+U to save a PNG image named in a save dialog.
- The exported image is a USGS-style slip-map panel: a white-background figure with rotated finite-fault patch rectangles, colored by slip amplitude, plus a color bar.
- Only direct finite-fault patches are exported (fault_id > 0 and patch_id > 0 with slip > 0).
- Auto-secondary deformation is ignored, matching the current v90 workflow.

Notes
- Patch color is based on the average absolute slip inside each patch.
- Patch size uses the stored stamp width/length and dip-projected surface width.
- The view auto-fits all exported patches into the figure.
