Add visualization picker to zone generation and unify tile colors

- Web map: multi-select picker in the generation bar (aspect, slope,
  positive openness, anisotropic openness, wavelet) passed to the API;
  the layer panel is restricted to the same shortlist (PANEL_VIZ) and
  a refresh button rebuilds the index when new layers appear on disk;
  jobs started outside the UI are now adopted into the visible queue
- Uniform colors across tiles: openness/anisotropic/sailore now store
  local z-scores, and all renderers use fixed ranges (0-3 sigma, SVF
  0-1 physical, slope 0-30 deg) instead of per-tile percentile stretches
- Ray-tracing falls back to CPU when VRAM is exhausted so openness and
  SVF no longer fail silently on shared GPUs
- build_index merges visualizations available at only one resolution
  into the displayed tile so in-progress layers stay visible
- 11 new tests (142 passing)

lidar_pipeline/tests/test_visualizations.py

@@ -215,3 +215,43 @@ class TestNodataPreserved:
             with rasterio.open(out) as src:
                 data = src.read(1)
             assert np.isnan(data[80:120, 80:120]).any(), f"{out.name} : trou disparu"
+
+
+def test_ray_trace_horizons_cpu_fallback_on_oom(monkeypatch):
+    """Sur OOM GPU, le ray-tracing désactive le GPU puis recommence sur CPU."""
+    import lidar_pipeline.visualizations as viz
+    import lidar_pipeline.gpu as gpu_mod
+
+    calls = {"n": 0}
+    disabled = []
+
+    def fake_core(dem, rows, cols, res, n_dirs, max_dist, radii_m=None):
+        calls["n"] += 1
+        if calls["n"] == 1:
+            raise RuntimeError("Out of memory allocating 600,000,000 bytes")
+        return ("pos", "neg")
+
+    monkeypatch.setattr(viz, "_ray_trace_horizons_core", fake_core)
+    monkeypatch.setattr(gpu_mod, "is_gpu_active", lambda: True)
+    monkeypatch.setattr(gpu_mod, "disable_gpu", lambda: disabled.append(True))
+    result = viz._ray_trace_horizons(None, 4, 4, 0.5, 8, 10)
+    assert result == ("pos", "neg")
+    assert calls["n"] == 2
+    assert disabled == [True]
+
+
+def test_ray_trace_horizons_reraises_non_oom(monkeypatch):
+    """Une erreur non-OOM n'est pas masquée par le repli CPU."""
+    import lidar_pipeline.visualizations as viz
+    import lidar_pipeline.gpu as gpu_mod
+
+    def fake_core(dem, rows, cols, res, n_dirs, max_dist, radii_m=None):
+        raise ValueError("autre erreur")
+
+    monkeypatch.setattr(viz, "_ray_trace_horizons_core", fake_core)
+    monkeypatch.setattr(gpu_mod, "is_gpu_active", lambda: True)
+    try:
+        viz._ray_trace_horizons(None, 4, 4, 0.5, 8, 10)
+        assert False, "ValueError attendue"
+    except ValueError:
+        pass