feat: add team admin CLI + migration 007 (settings, cooldowns, create_team RPC)

New `gstack team` CLI with create, members, set subcommands.
Migration adds team_settings (admin-only), alert_cooldowns (edge-fn
dedup), and create_team() SECURITY DEFINER RPC for atomic team +
first member creation. 9 tests.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

bin/gstack-team

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# gstack team — team admin CLI
+# Delegates to lib/cli-team.ts via bun
+
+GSTACK_DIR="${GSTACK_DIR:-$(cd "$(dirname "$0")/.." && pwd)}"
+exec bun run "$GSTACK_DIR/lib/cli-team.ts" "$@"