feat: container management tools in tools/

Shell scripts for build, start, stop, restart, nuke, logs, status.
Shared helpers in _common.sh (colours, compose detection, project root).
Updated CHEATSHEET.md with new tool references.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tools/logs

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+# Tail container logs.
+# Usage: tools/logs [N]
+
+# shellcheck source=tools/_common.sh
+source "$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/_common.sh"
+
+tail_n="${1:-30}"
+podman logs -f --tail "$tail_n" "$CONTAINER_NAME"