svc-vision: camera live view, moved from app-flutter's test tool

Camera-agnostic (--camera auto finds any V4L2 capture device and finds it
again after a replug; non-MJPEG cameras are encoded), says when the camera
is unavailable, paced per decision 28. Python, standard library only.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz

scripts/deploy.sh

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+# Install svc-vision on an Orin as the yukart-vision service.
+#
+#   usage: scripts/deploy.sh [host]        (default: mikkeli-orin-nano)
+#
+# Python 3.10 and the standard library only: nothing to build. The host needs
+# gst-launch-1.0 (GStreamer, part of JetPack) and v4l2-ctl (v4l-utils).
+set -euo pipefail
+
+HOST="${1:-mikkeli-orin-nano}"
+cd "$(dirname "$0")/.."
+
+ssh "$HOST" 'set -e
+  command -v gst-launch-1.0 >/dev/null || { echo "missing gst-launch-1.0" >&2; exit 1; }
+  command -v v4l2-ctl >/dev/null || { echo "missing v4l2-ctl (v4l-utils)" >&2; exit 1; }
+  python3 -c "import sys; assert sys.version_info >= (3, 10)"
+  mkdir -p ~/infra/svc-vision'
+scp -q src/liveview.py "$HOST:infra/svc-vision/liveview.py.new"
+scp -q deploy/yukart-vision.service "$HOST:infra/svc-vision/yukart-vision.service"
+ssh "$HOST" 'set -e
+  mv ~/infra/svc-vision/liveview.py.new ~/infra/svc-vision/liveview.py
+  sudo install -m 0644 ~/infra/svc-vision/yukart-vision.service /etc/systemd/system/yukart-vision.service
+  sudo systemctl daemon-reload
+  sudo systemctl enable yukart-vision.service >/dev/null
+  sudo systemctl restart yukart-vision.service
+  sleep 2
+  systemctl --no-pager --lines=5 status yukart-vision.service'