Release v0.8.0 — Portainer-first install, in-app guide

- Install from Portainer with no command line: paste the compose, set a
  folder and a password, deploy. Inspector creates its own config and
  detects Docker socket permissions by itself.
- Illustrated how-to guide inside the app (Help tab) and in the repo.
- Containers added in the UI are watched right away, no restart.
- maintenance_window switch on the container form.
- README with logo and screenshots; INSTALL rewritten for Portainer.

docker-entrypoint.sh

@@ -0,0 +1,38 @@
+#!/bin/sh
+# Inspector container entrypoint.
+#
+# Started as root (the default): find the group that owns the Docker socket,
+# make the mounted folders writable, then drop to an unprivileged user with
+# that group added. No DOCKER_GID / group_add needed.
+#
+# Started as non-root (compose `user:` / older group_add setups): run as-is.
+set -e
+
+if [ "$(id -u)" != "0" ]; then
+  exec "$@"
+fi
+
+PUID="${PUID:-1000}"
+PGID="${PGID:-1000}"
+SOCK=/var/run/docker.sock
+
+groups="$PGID"
+if [ -S "$SOCK" ]; then
+  sock_gid="$(stat -c %g "$SOCK")"
+  groups="$groups,$sock_gid"
+else
+  echo "warning: $SOCK is not mounted; Inspector cannot see any containers" >&2
+fi
+
+# Mounted folders are often created by Docker as root. Hand them (not their
+# contents) to the runtime user so Inspector can write config, logs and data.
+for d in /app/config /app/logs /app/data; do
+  if [ -d "$d" ] && [ "$(stat -c %u "$d")" != "$PUID" ]; then
+    chown "$PUID:$PGID" "$d" 2>/dev/null || echo "warning: could not chown $d" >&2
+  fi
+done
+if [ -f /app/config/config.yml ] && [ "$(stat -c %u /app/config/config.yml)" != "$PUID" ]; then
+  chown "$PUID:$PGID" /app/config/config.yml 2>/dev/null || true
+fi
+
+exec setpriv --reuid="$PUID" --regid="$PGID" --groups="$groups" "$@"