Initial commit: scan_web integrated recording UI

FastAPI backend + vanilla JS frontend for LiDAR/camera startup, camera
settings, and rosbag recording, unifying the previous scan_gui/scan_gui_dual/
scan_gui_triple desktop tools into one web app.

run_scan_web.sh

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+# Launches scan_web: sources the ROS overlays the backend's ManagedProcess
+# commands need to be able to `ros2 launch`/`ros2 bag record` against, then
+# runs the FastAPI app with a single uvicorn worker (required — see
+# backend/app.py: the rclpy context + ProcessManager registry live in
+# process memory and must not be duplicated across workers).
+# NOTE: no `-u` (nounset) — ROS's setup.bash references unset variables
+# internally (e.g. AMENT_TRACE_SETUP_FILES) and isn't nounset-safe.
+set -eo pipefail
+
+HOME_DIR="/home/gardentech"
+
+source /opt/ros/humble/setup.bash
+# fast_ws deprecated (2026-08-05) — it was the pre-3-camera predecessor to
+# fast_dual_ws and never had its own livox_ros_driver2 build (only chained
+# to lidar2_ws/install as an underlay). Source lidar2_ws directly.
+source "${HOME_DIR}/lidar2_ws/install/setup.bash"
+source "${HOME_DIR}/camera2_ws/install/setup.bash"
+if [ -f "${HOME_DIR}/fast_dual_ws/install/setup.bash" ]; then
+  source "${HOME_DIR}/fast_dual_ws/install/setup.bash"
+fi
+# rtk_ws intentionally not sourced yet — GPS/RTK integration is Phase 1
+# Milestone 2, unused until then.
+
+cd "${HOME_DIR}/scan_web/backend"
+exec python3 -m uvicorn app:app --host 0.0.0.0 --port 8000 --workers 1