fix(sync): create SYNC_BASE_PATH at startup before watching

The prod Dockerfile creates /var/lib/romm/sync at build time, but if a
user overrides SYNC_BASE_PATH to a path that doesn't exist (or runs the
dev entrypoint, which never created the default), watchfiles fails to
start because its target directory is missing. Have both entrypoints
mkdir -p the resolved path before handing it to watchfiles.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docker/init_scripts/init

@@ -249,6 +249,7 @@ start_bin_watcher() {
 start_bin_sync_watcher() {
 	info_log "Starting sync folder watcher"
 	local sync_base_path="${SYNC_BASE_PATH:-/var/lib/romm/sync}"
+	mkdir -p "${sync_base_path}"
 	if [[ ${OTEL_SDK_DISABLED:-false} == "true" ]]; then
 		watchfiles \
 			--target-type command \