Portable Ithaca capture node: one install for every Jetson

Extract the install that was applied by hand to the Jetson Nano into a single
checkout that builds itself for whatever Jetson it lands on.

The two nodes on the rig share no JetPack — tegra210 caps at 4, tegra234 needs
5+ — so nothing binary is portable between them. The source and the procedure
are: install.sh detects the platform (L4T / JetPack / SoC), installs deps,
builds the OrbbecSDK and the preview server from source locally, and generates
a per-user config and systemd unit. The tested bridge.py ships verbatim; all
machine-specific paths live in the generated config, so it stays unmodified —
its one hardcoded path is made home-relative.

The retired GStreamer/RTSP target is dropped: the direct route encodes no video.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

systemd/ithaca-bridge.service.in

@@ -0,0 +1,21 @@
+[Unit]
+Description=Ithaca WebSocket bridge (Jetson node)
+Documentation=file:@REPO@/bridge/bridge.py
+After=network.target usbfs-memory.service
+Wants=network.target
+
+[Service]
+Type=simple
+User=@USER@
+WorkingDirectory=@REPO@/bridge
+ExecStart=/usr/bin/python3 -u @REPO@/bridge/bridge.py @REPO@/bridge/config.json
+Restart=always
+RestartSec=5
+KillSignal=SIGINT
+TimeoutStopSec=20
+StandardOutput=journal
+StandardError=journal
+SyslogIdentifier=ithaca-bridge
+
+[Install]
+WantedBy=multi-user.target

systemd/usbfs-memory.service

@@ -0,0 +1,12 @@
+[Unit]
+Description=Raise usbfs_memory_mb for Orbbec depth cameras
+After=sysinit.target
+Before=multi-user.target
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecStart=/bin/sh -c 'echo 1000 > /sys/module/usbcore/parameters/usbfs_memory_mb'
+
+[Install]
+WantedBy=multi-user.target