Upgrade colormaps to Crameri scientific palette and fix IGN location map

- Replace RdBu_r with Crameri roma for all 6 relief-family colormaps
  (curvature, mslrm, lrm, tpi, sailore, aniso_open): perceptually
  uniform, CVD-friendly, dark center makes near-zero values visible
- Replace hsv with twilight for aspect: perceptually uniform cyclic
  colormap with no hue discontinuity
- Add cmcrameri dependency (falls back to RdBu_r if unavailable)
- Fix IGN location map: pass min_zoom=8 to download_ign_tiles so zoom
  10 context maps work (was hardcoded to min_zoom=15, blocking the
  loop entirely for zoom_level=10)
- Expand location map context from 3x extent to 80km fixed radius for
  better regional context at zoom 10
- Remove dead code: flow colormap entry, _nice_scale dead loop,
  aspect='auto' in location map imshow, outdated PDF report order list
- Fix SVF docstring: 8 directions → 16 directions

lidar_pipeline/visualizations.py

@@ -1287,7 +1287,7 @@ def generate_flow(dem_file, basename, vis_dir, resolution, shared=None):
 def generate_svf(dem_file, basename, vis_dir, resolution, shared=None):
     """Sky-View Factor - fraction of sky visible from each point (GPU if available).
 
-    SVF = average of cos²(horizon_angle) across 8 directions.
+    SVF = average of cos²(horizon_angle) across 16 directions.
     High SVF (near 1) = open sky (ridgetop, plateau)
     Low SVF (near 0) = enclosed sky (valley, deep trench)