M2c-dev: development compose stack, backup job, Firebase setup docs

infra/dev: compose stack on the Mac (server kvitt-server:dev, on-demand backup),
.env.example, build/up/logs/backup/copy-google-services scripts. No Caddy, no TLS
(debug builds accept http to private LAN addresses, AC-2.8). Bind-mounted data.
infra/backup: alpine 3.24.2 image and backup.sh (SPEC 10.9; Drive upload skipped
when RCLONE_FOLDER_ID is empty). infra/README.md for the dev stack and Firebase.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

infra/dev/logs.sh

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+# Follows the development stack's logs. Extra arguments go to `docker compose logs`
+# (for example: infra/dev/logs.sh --tail 100 server).
+set -euo pipefail
+# shellcheck source=lib.sh
+. "$(dirname "$0")/lib.sh"
+
+compose logs -f "$@"