Add scan-editing CLI and alignment tests; extend Manual Alignment correlation

Continues the Manual Alignment work: refines the FFT cross-correlation and
mask handling, adds sras_edit_scans.py (drop/renumber bad angle scans),
tools/test_alignment.py (registration ground-truth suite), and a rotating
test fixture in make_test_sras.py.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

sras_viewer_requirements.txt

@@ -1,3 +1,11 @@
 PyQt6==6.10.2
 numpy==2.4.1
 matplotlib==3.10.8
+scipy==1.18.0
+# Angle alignment only: masked FFT phase correlation, which registers scans
+# whose valid (scanned) regions differ in shape — see sras_compute's
+# _masked_shift.
+scikit-image==0.26.0
+# Optional: a faster rfft backend for the RF/FFT images (FFT Options -> pyFFTW).
+# The viewer falls back to scipy.fft when it is not installed.
+pyFFTW==0.15.1