Port the SAR3D background gate, CLEAN and object boxes from Multi_depthnorm_clean

- BG_GATE_ENABLE: frame peak over its median background (sar3d_background); the
  GUI scales the frame with bg_gate_gain and its cloud threshold.
- SAR_CLEAN_ENABLE: CLEAN of a one-frame aperture on a 4x10x4 cm search grid over
  the whole scene; objects in their own scale (sar3d_objects).
- SAR_MARK_ENABLE: boxes by class around object groups (sar3d_marks), with the
  legend under the views.
- SAR_VOXEL_M as three steps X/Y/Z with the notebook defaults 0.025/0.02/0.02.
- GPU backend: image/download/load/project API, per-plane block reduction for the
  maximum, depth gate without FMA; sar3d host code built with -ffp-contract=off.
- References regenerated from notebook cells 1 and 5, with new CLEAN scenes and a
  synthetic box-rule case; docs updated.

python_app/orchestration/live_processing_config.py

@@ -53,11 +53,13 @@ class ProcessingLiveConfig:
     gpr_visible_z_min_m: float = 0.0
     gpr_visible_z_max_m: float = 14.0
     # 3D SAR (sar3d processor) parameters, named after the reference notebook
-    # Multi_antenna_demonstrate_depthnorm.ipynb (SAR_FRAME_RADIUS, BP_GROUND_DEPTH_M, ...).
+    # Multi_depthnorm_clean.ipynb (SAR_FRAME_RADIUS, BP_GROUND_DEPTH_M, ...).
     # The band, depth gate, antenna selection, speed and look angle are the
     # shared gpr_* fields.
     sar3d_frame_radius: int = 0
-    sar3d_voxel_m: float = 0.02   # SAR_VOXEL_M, one edge for X, Y and Z
+    sar3d_voxel_x_m: float = 0.025   # SAR_VOXEL_M, the voxel steps along X, Y and Z
+    sar3d_voxel_y_m: float = 0.02
+    sar3d_voxel_z_m: float = 0.02
     sar3d_bp_ground_depth_m: float = 1.25
     sar3d_comp_range_power: float = 0.3
     sar3d_use_compensation: bool = True
@@ -66,6 +68,8 @@ class ProcessingLiveConfig:
     sar3d_y_min_m: float = -0.5
     sar3d_y_max_m: float = 2.0
     sar3d_z_size_m: float = 0.0
+    sar3d_bg_gate_enabled: bool = True   # BG_GATE_ENABLE: peak-to-background ratio for the display
+    sar3d_clean_enabled: bool = True     # SAR_CLEAN_ENABLE: CLEAN of a one-frame aperture into objects
     # When true, the C++ data_processor ignores socket-supplied vlc updates
     # and keeps using `gpr_speed_m_s` from this file.
     ignore_socket_speed: bool = False