User Guide — moved

The bridge's user guide is now a set of pages under docs/guide/, organised by what you are trying to do rather than as one long file:

• Guide index — start here; the three control paths, and what was verified
• Tour of the UI — navigation, the top bar, and all seventeen tabs
• Control and write safety — the three gates, battery force, the audit trail
• Scheduler — triggers, conditions, actions, targets, exits, outcomes
• Home Assistant and MQTT — topics, the 21 entities, shared brokers
• Multi-gateway and sites — gateways, mocks, sites and meters
• History, costs and tariffs — retention, the Sankey, tariffs, backups

For installation and upgrading, see INSTALL.md.