dashboard: unified tabbed UI for Main/Charts/Historical/Automation/Configuration

- Replace the previous single-page layout with five top-level tabs.
- Main Dashboard: icon cards for Inverter, Battery, Grid, Solar, Load,
  Environment; click any card to drill into a detail view.
- 24-hour combined power-flow line chart on the main page.
- Charts Dashboard: 30-day bar charts for battery, grid, inverter, solar.
- Historical Dashboard: 1-year bar charts plus daily totals chart.
- Automation Dashboard: existing rule editor/log moved into its own tab.
- Configuration Dashboard: inverter, system time/date, network, MQTT, and
  backup sections with sub-tabs.
- Use Chart.js via CDN; adapt JS to actual /api/history and /api/energy
  response shapes.

Author: Jeremy Ewing